He called them "filthy" in a Facebook post and said they "have no place in western civilization."
"The more muslim savages we allow into america - the more terror we will see," another of his posts stated.
Feigin, 41, freely admits to having harsh opinions, a "big mouth" and being "a disaster on social media."
But he says he knows the difference between a threat and a constitutionally protected opinion and is careful not to cross that line.
However, that's precisely what authorities say he did last September when he allegedly called a Los Angeles mosque and threatened to kill its members.
Officials from the Los Angeles Police Department and then-California Attorney General Kamala Harris's Office held a press conference in October announcing Feigin's arrest on a felony hate crime charge.
They showed reporters blown-up photos of guns and ammunition seized from Feigin's house, and a spokesperson for the mosque who joined police on stage said he feared the suspect had been plotting a "Columbine-type event."
A year later, however, there is significant evidence suggesting police may have charged the wrong man, according to a CNN review of hundreds of pages of court records and interviews with participants in the case.
Prosecutors have persisted in their case against Feigin despite dwindling and contradictory evidence, CNN found. At the same time, authorities have declined to pursue charges against a "second suspect" who they now concede is responsible for a belligerent anti-Muslim voicemail left at the mosque, which they once attributed to Feigin and originally viewed as a key piece of evidence against him. That man is the 27-year-old son of a Los Angeles County Superior Court judge.
What once appeared to be a straightforward hate crime prosecution is shaping up to be a high-stakes legal battle involving not only an alternate suspect, but allegations of sloppy police work, prosecutorial misconduct and political opportunism being leveled by the defense in court filings.
State prosecutors and LAPD officials declined comment for this article, citing the pending prosecution against Feigin.
A Canadian conservative website called The Rebel posted a video last month detailing recent developments in Feigin's case. But the matter has received little attention elsewhere since his high-profile arrest last year.
The following account is based on police reports, phone records, audio recordings, interview transcripts and other material obtained by CNN.
'Can't be a coincidence'
When Muhammad Popote arrived for work at the Islamic Center of Southern California on September 19 of last year, there was a message waiting on the center's voicemail.
"I hope you [expletive] Muslim rats either leave the US or dump your stupid [expletive] religion," the unknown caller said.
The following day, Popote answered the phone and heard what he would later tell police was the same male voice he recognized from the message a day earlier. Popote said the caller uttered the same derogatory phrase as the day before.
Popote, 19, dialed 911 minutes later to report the alleged threat.
"He said that he's going to annihilate Muslim rats like us," Popote told the operator, according to a recording of the call.
Popote said he suspected the unknown caller was the same person who had recently made some insulting posts on the center's Facebook page.
His name is Mark Feigin, he told the operator.
"He seems to be the racist type and he fits the profile exactly," Popote said.
He told the operator he had done some investigating of his own; he had called Feigin's cell phone and said the voice sounded the same as the threatening caller. He was hoping LAPD could find out for sure, he said.
Popote added that he was "fairly certain" of the connection. It "can't be a coincidence," he said.
The case landed on the desk of Detective Kenneth Bryant of the LAPD's Major Crimes Division.
Bryant looked at Feigin's Facebook page and the real estate company page with Feigin's phone number, as Popote had. The detective also ran Feigin's name through a firearms database and discovered the suspect was the registered owner of multiple guns.
On October 18, Bryant filed a search warrant affidavit asking a judge for access to Feigin's phone records, Facebook account information and guns. The judge granted the request.
But police and prosecutors did not wait to obtain access to the records they sought.
One day after the search warrant was approved, Feigin was arrested at gunpoint as he drove away from the trailer park outside Los Angeles where he lives.
It was his first time being handcuffed or riding in the back of a police car, he would later tell detectives.
'A big mouth'
Feigin immediately waived his rights and agreed to speak with the police. He did so bluntly, using the F-word with abandon, according to a transcription of the interview. He acknowledged that he routinely posted "harsh" comments on the Internet, many of them directed at Muslims.
"I'm not really a fan of Islam. I mean, I don't like their religion," Feigin said. He added, "Somebody has to say something about these people because they're [expletive] dangerous."
The suspect admitted to having "a big mouth" and being "a disaster on social media." But he also told Bryant he learned the difference between an opinion and a threat in a high school Constitution class and it was a lesson he had not forgotten.
Feigin volunteered that he'd been visited by the FBI about six months earlier due to provocative posts following the 2015 Paris terror attacks. He argued in the posts that the French got what they deserved for having lax security and for allowing so many immigrants into the country.
He told Bryant the agents said his opinions were "stupid and crazy," but were also protected free speech under the First Amendment.
"Just don't say you're going to kill anybody, hurt anybody, blow up a building the next day," he said the agents advised.
Bryant told Feigin the reason for his arrest had nothing to do with Facebook posts or any other online activity.
"I can tell you that a hundred percent," the detective said.
He asked Feigin whether he recalled making any phone calls to the Islamic Center.
"I don't," Feigin replied.
When Bryant told him he had a recording of a voicemail he'd allegedly left, Feigin asked the detective to play it to perhaps jog his memory.
Bryant played the message left on September 19 about "Muslim rats."
Feigin acknowleged that the caller's voice sounded like his own, but again insisted he had no recollection of making the call.
"What the [expletive] was I thinking?" he asks aloud at one point. "Maybe I was drunk. One night I got [expletive] wasted. By the way, it's unlike me to do that."
Bryant told Feigin the call was made during the day.
The suspect then told the detective there was one way to be sure.
"You can check my phone and you can find out if it was me," Feigin said. "So, it's not a big deal."
"This call is not what got you in trouble," Bryant said.
The real trouble, the detective said, stemmed from another call to Popote at the Islamic Center the following day.
"He says that you definitely made a threat to him," Bryant explained, "and that's what we're going on."
Bryant asked Feigin whether he remembered making that call.
"No, I don't,'' he said.
"I wouldn't threaten anybody," Feigin added. "I don't want to risk getting arrested like I am now...for no reason, for basically being an asshole."
Feigin steadfastly denied any memory of calling the Islamic center throughout the interview. But he eventually accepted Bryant's premise that the voice on the recording was his and acknowledged, therefore, that he must have.
Feigin, who is Polish by birth, at one point told Bryant that his Eastern European heritage made him "hotheaded."
"We're all [expletive] hotheaded," he said. "Everyone in Eastern Europe tells you they're gonna kill you every five seconds, you know. But they don't really act on it."
Feigin added that he wouldn't make such a threat in the US, because "it's illegal."
Bryant seized on Feigin's admission that he was hotheaded.
"What you just said to me is exactly what I think happened," the detective told Feigin.
As the interview is ending, Bryant tells Feigin he's going to have turn over his personal possessions, including his phone and credit cards, as part of the process of being booked into jail. Feigin drops one last F-bomb.
"This is a [expletive] disaster," he said.
Feigin was charged with a felony for allegedly threatening Popote during the September 20 phone call and with a misdemeanor for allegedly leaving the harassing voicemail on the 19th.
He has not been charged with a crime in connection with any of the weapons featured in the blown-up photograph displayed for reporters at the press conference. According to a prosecution court filing, six of the guns were registered to Feigin and two were registered to his father.
In December, two months after Feigin's arrest, police obtained his phone records.
In them -- or not in them, actually -- was a surprise.
There was no evidence he'd called the mosque. Not on the day the harassing voicemail was left. Not on the day of the threat call.
'Your religion is stupid'
But the Islamic center's phone records, which police had also obtained in December, did show an incoming call at the time Popote reported the harassing voicemail on September 19.
The minute-long call came in at 8:26 a.m. from a local number.
Three months would pass before Bryant realized the significance of that number. That happened in March during a case briefing in which he was told by fellow detectives of another suspect under investigation for allegedly making harassing calls to a mosque.
Bryant listened to a recording of that suspect calling the Burbank Islamic Center and noted that the voice "sounded similar" to the September 19 voicemail he attributed to Feigin.
Detectives working the Burbank mosque case had identified their caller as Michael Slawson.
Bryant checked the Islamic center records and discovered that the September 19 voicemail in his case came from Slawson's phone as well.
The detective called Slawson and attempted to interview him. Slawson declined to talk and referred him to his attorney, Dominic J. Trutanich, the brother of former Los Angeles City Attorney Carmen Trutanich.
Bryant arranged for he and his partner to question Slawson a couple weeks later at Trutanich's office in San Pedro.
Slawson was soft-spoken and unfailingly polite to the detectives, repeatedly addressing each as "sir" when he answered their questions, according to audio of the interview listened to by CNN.
He admitted to calling the Islamic center and multiple other mosques around Southern California. He told the detectives he had done so to express his vehement opposition to Islam.
"Your religion is violent. Your religion is stupid. That's what I said," Slawson recounted.
He identified himself as a "religious Christian" who engages in home Bible study and watches a lot of online videos from the Faithful Word Baptist Church, which is based in Phoenix.
But he told the detectives that he'd never broken the law with any of his calls.
"I'm very interested in politics...and I have, you know, aspirations of doing things in my own life," Slawson said. "So I don't step outside of those things by breaking the law."
The detectives spent 15 minutes debating Slawson about what constitutes harassment, but never directly confronted him on whether he'd made the threatening call to the Islamic center, according to the recording.
Bryant asked Slawson whether it would surprise him to learn that police had a recording of one of his phone calls.
"No," Slawson replied.
But the detectives did not confront him with the recording, as they had Feigin.
They didn't ask him about the "Muslim rats" phrase used in the voicemail they now knew he'd left and the same phrase being used in the threat call the following day.
They never confronted him with Popote's statement that the voice on the voicemail and the voice on the threat call belonged to the same person.
Still, the detectives told Slawson his conduct was potentially problematic.
"You're very, very close, if not slightly over the line, when it comes to breaking certain laws," said Detective James Dickson, Bryant's partner.
Dickson's comment seemed to be referring to the misdemeanor of making annoying phone calls as opposed to the more serious felony of making threats.
"A reasonable person would assume that what you were doing was pretty darn annoying," the detective said.
At that point, Slawson's lawyer chimed in. He asked whether the detectives were being a little overzealous in their effort to investigate offensive words directed at Islam.
"It's kinda healthy to have kids expressing their views. That's what the country's built on," Trutanich said. "I don't have the balls to do it -- he did."
The lawyer added, "We probably all think it."
'Sort of being persecuted right now'
It is unclear how much detectives knew about Slawson prior to their interview in April.
Slawson told the detectives during the interview that he worked at a bank in downtown Los Angeles. According to public records, he also has a security guard license and a permit for carrying a police-style baton.
His phone records show that he called numerous mosques in Southern California and elsewhere during the two-day period when the harassing and threatening calls were made to the Islamic center in Los Angeles.
The records also show that he placed several calls to Stag Arms, a manufacturer of AR-15 rifles, four days prior to leaving the message at the Islamic center.
The church Slawson told the detectives he followed describes itself on its website as an "old-fashioned, independent, fundamental, King James Bible only, soul-winning Baptist church."
Pastor Steven Anderson is its leader. Anderson drew controversy in 2009 when he said he was going to pray for the death of President Barack Obama and again last year when he said the Orlando nightclub massacre was "good news" because it had ridded the world of "pedophiles."
Anderson has been critical of various other religions, including Islam, which he labels a fraud. Anderson has preached that Islam is a "wicked" religion, but that doesn't mean all Muslims are evil.
"It's not their fault in many cases that they've been brought up and are deceived and ignorant from birth," he said, according to a transcript of a June 15, 2015, sermon published on the church's website. "They're waiting for YOU to bring them to the gospel."
In an interview with CNN, Anderson said Slawson left him a voicemail earlier this year in which he said he was "sort of being persecuted right now" and asked for advice.
The call was placed in March, after he'd come under investigation in the Burbank Islamic Center case, but before his interview with Bryant and Dickson.
"I'm, unfortunately, being put in a situation where I'm having to be afraid of what's going to happen at the hands of the police, who are actually threatening to, uh, well, yeah, I'll leave it at that," Slawson said in the message.
He left another message a few months earlier asking for help in choosing a Bible, Anderson said.
Anderson said he did not return either call, but saved the voice messages, which he played for CNN.
"I have no clue who this guy is," the pastor said. "I have never met him or talked to him."
It's apparent that religion was on Slawson's mind on September 20, the day the threat call was made to the Islamic center.
That evening, Slawson sat down in front of a camera in what appears to be his apartment. He wore a white T-shirt and a ceiling fan spun overhead.
He began live streaming on YouTube, then read from the Bible, uninterrupted, for over an hour.
Neither Slawson nor Trutanich responded to multiple attempts to reach them for comment for this story.
Judge John Slawson, Michael's father, declined to discuss the situation in detail.
"It's a family matter that we're trying to work through, and we'll go from there," the elder Slawson said in a brief telephone interview with CNN.
'Deliberately attempting to prosecute an innocent man'
Feigin has grown increasingly impatient and frustrated by what he sees as a miscarriage of justice.
In May, he posted a video on YouTube arguing that he'd been falsely charged and soliciting money for his legal defense. As of Thursday, he'd raised $227 from seven contributors.
Asked what prompted him to falsely concede that he'd left the voicemail at the Islamic center, Feigin told CNN there were a couple factors at play.
First, he said he'd grown up in a conservative family and had always associated the police with honesty and integrity. Therefore, when Bryant told him that he placed the call, he assumed the detective was telling the truth, even though he couldn't remember making it.
Adding to the mix, Feigin said, was that he'd just recently returned home from a trip abroad. He'd taken a sleep aid the night before, slept for only three hours, and awoke feeling groggy.
He insisted he was not responsible for the threat call and, therefore, refused an offer from the prosecution that would have allowed him to plead guilty without doing any time in prison.
"I would not be going through this nightmare, risking years in prison, if I did it," Feigin said. "It's been the worst experience of my life."
Despite the discovery that Slawson was responsible for the hateful voicemail, the charges against Feigin remain the same. In the criminal complaint against him, the Facebook posts, which Det. Bryant repeatedly told Feigin were not criminal in nature, have replaced that phone call and another one made in 2015 that also was falsely attributed to him.
Police have been unable to trace the number used to make the threat call back to anyone. The number is assigned to Citrix Corporation for use in the remote desktop software LogMeIn. Bryant requested information about the number from Citrix in late April but the company said its records pertaining to 2016, when the call was made, had been purged.
At Feigin's request, Bryant asked the FBI to help trace the number but was told by an agent that such "roadblocks" were a common problem and there was nothing the bureau could do to help.
The prosecution appears to be basing the felony threat charge against Feigin, in part, on Popote's identification of him as the caller.
They are doing so despite the fact that Popote had initially said the person who left the September 19 voicemail --now known to be Slawson -- and the threat caller sounded to be one and the same.
In May, Deputy Attorney General Natasha Howard, the prosecutor, along with Bryant and Dickson, reinterviewed Popote at the Islamic center. Though they knew by then that Slawson was the voicemail caller, the police report documenting the interview makes no mention of them telling Popote that someone other than Feigin could be responsible for that call.
In a brief interview with CNN, Popote said neither police nor prosecutors have ever questioned him about anyone other than Feigin or provided any information about a "second suspect" harassing or threatening the center.
He declined further comment, saying he'd been instructed not to discuss the matter -- he would not say by whom.
Prosecutors will also likely use Feigin's statements to Bryant, which they appear to consider a confession, and a subsequent statement to an LAPD lieutenant during a phone call following his arrest. According to a police report, Feigin was complaining to Lt. Anita McKeown that the LAPD was ruining his life when he allegedly blurted out, "I yelled at the guy on the phone, and yea[h] maybe I meant it...I'm Polish we say stuff."
Slawson, meanwhile, has not been charged with any crime.
Majdi Bitar, director of the Burbank Islamic Center, said he sent police a recorded telephone call and voicemail message in which the caller -- later identified as Slawson -- told Muslims they are "animals" who aren't welcome in the United States and that they should all "go to hell."
"This guy, he kept on calling," Bitar said in an interview with CNN. "He was always trying to get me to react."
Bryant's colleagues in the Major Crimes Division submitted the case to the Los Angeles City Attorney's Office but it was rejected due to "lack of sufficient evidence," according to court records.
Howard, the deputy attorney general prosecuting Feigin, dismissed the notion that Slawson could be responsible for the threat call in her case, in essence, because he said he didn't do it.
In a recent court filing, Howard noted that Slawson was "very specific" that he only used his cell phone to make calls to mosques, that he never called from work or used programs such as LogMeIn and that his cell phone records show no such call.
"Taking into account all of this information," she wrote, "it becomes crystal clear that Slawson is not responsible for the felony criminal threat charged in this case."
Howard did not address the use of the phrase "Muslim rats" in Slawson's voicemail on the 19th and a day later by the threat caller. She mischaracterized the contents of the 911 call in court documents and omitted Popote's statement that the caller said he wanted to "annihilate Muslim rats."
In August, Feigin's lawyer, Caleb Mason, filed a sweeping motion assailing the prosecution's case as sloppily investigated and hastily charged.
The result, he said, was that Feigin was publicly smeared as "a dangerous would-be mass killer."
Mason, a former assistant US attorney, accused the attorney general's office of "deliberately attempting to prosecute an innocent man for the acts of a guilty man." He argued the evidence in the case leads to the "unavoidable inference[s]" that Feigin is being unfairly prosecuted because he's an anti-Muslim conservative and that Slawson is being protected because his father is a Superior Court judge.
Mason raised his concerns and allegations in a motion seeking a court order for access to "all communications" between police and prosecutors that could shed light on "unlawful motives" behind the prosecution.
Howard countered that Mason's motion is "a series of misstatements and inaccuracies in an attempt to try and shift the focus away from [Feigin] and towards someone else."
His argument, she wrote, "is heavy on speculation, guesses and theories and contains little to no facts to support them."
Howard wrote that the defense had failed to produce any evidence that Feigin had been unfairly targeted for prosecution and dismissed the notion that Slawson had been given a pass because his father is a judge.
"Nothing could be further from the truth," she wrote.
Mason also raised questions about the "unusual and unexplained" role of then-Attorney General Kamala Harris's office and the prospect that the case was brought for some "political benefit."
Typically, local prosecutions are handled by the county district attorney in a given jurisdiction, not the state attorney general's office. In his court filing, Mason cited language in a plea offer extended to Feigin which he said suggested "improper political motives" behind the prosecution. The deal required, among other things, that Feigin "renounce the KKK and the alt-right."
Mason called the plea offer "bizarre" in his court filing, noting that Feigin "has no connection to the KKK, and none was ever alleged." He added that Feigin's family is Jewish and Catholic, both targets of the Klan.
The former prosecutor also questioned the condition regarding the "alt-right."
"[S]ince when does a prosecutor demand that a defendant 'renounce' his political beliefs as a condition of avoiding prison," Mason wrote. "The answer is simple: We don't do that, not in this country."
Nathan Barankin, who served as Harris's chief of staff during her tenure as California attorney general and holds the same post in her Senate office, brushed aside the suggestion of any impropriety.
He said Harris had been meeting with law enforcement officials around California for more than a year due to an uptick in hate crime reports. He said Harris made clear her office's interest in taking on such cases, in part to send a message to the victims of such crimes that they would be protected.
The timing of the charges being filed in October -- shortly before her then-looming US Senate election -- had only to do with the crime being committed in September, Barankin said.
At the press conference announcing the charges, LAPD Commander Horace Frank didn't seem entirely clear on why the case had been filed by the attorney general.
Asked by a reporter why the case had not gone to the district attorney as a "conventional prosecution," he repeated the question to Howard.
"It could," she said.
Frank turned back to reporters.
"It could," he repeated. "But this is the route that we chose."
"Is there a reason for that?" a reporter asked. "It's unusual."
"I guess the seriousness of the crime," Frank replied.
Los Angeles Superior Court Judge Dorothy B. Reyes earlier this month denied Mason's request for enhanced access to communications between police and prosecutors. She did so without prejudice, meaning she could revisit the issue.
A preliminary hearing, at which a judge will determine if there is sufficient evidence for the case to go to trial, is set for Monday.