Jordan Hill, 18; Tesfaye Cooper; 18; Brittany Covington, 18; and Tanishia Covington, 24, have each been charged with a hate crime, felony aggravated kidnapping, aggravated unlawful restraint and aggravated battery with a deadly weapon.
Hill, Cooper and Brittany Covington also face charges of residential burglary. Hill also faces charges of possession of a stolen motor vehicle.
Video of the torture has stunned the country, not just because of the graphic abuse, but because of the comments made by some of the assailants.
"*F*ck Donald Trump!" one attacker shouted in the video. "F*ck white people!"
The teen was tied up for four or five hours, Cmdr. Kevin Duffin of the Chicago Police Department told reporters. The victim will recover from his injuries and is at home with his parents, police said.
The teen's brother-in-law spoke briefly with reporters Thursday night.
"We're so grateful for all the prayers and efforts that led to the safe return of our brother. We're fully aware of the charges being brought against the offenders. At this time, we ask for continued prayers for all those involved, for our family's privacy as we cope and heal," David Boyd said, reading a statement.
Boyd said the teen is doing as well as can be expected. He told the media that everyone in the family has seen the video, but he didn't comment further on it.
Duffin said the department sought hate crime charges because of the victim's diminished mental capacity, the fact that the four suspects tied him up and the racial epithets heard on the video. The victim apparently is white; the suspects are African-American.
The suspects will appear in court Friday.
30 minutes of horror
Video of the attack shows the 18-year-old victim cowering in a corner of a room, tied up with his mouth bound in plastic. His eyes exude fear as his attackers get ready for their next act.
One assailant slashes his sweatshirt with a knife. The young woman streaming the abuse on Facebook Live repeatedly turns the camera back to herself.
An attacker then takes a knife to the victim's head, carving a patch off his scalp.
For the next 25 minutes, the abuse continues for the world to see. The victim is repeatedly kicked and punched, but his screams are apparently ignored.
The young woman broadcasting the attack appears dismayed that she's not getting more attention online.
"Y'all not even commenting on my s***," she tells a friend during the live stream.
Debate over 'Black Lives Matter'
Many who saw the video have blamed the Black Lives Matter
movement. Within 24 hours, the hashtag #BLMKidnapping was mentioned more than 480,000 times
But on Thursday, police said they have not seen any connection to the Black Lives Matter activist group, contrary to some reports on social media.
Neither the Black Lives Matter national organization nor its Chicago chapter responded to CNN's request for comment Thursday.
But DeRay Mckesson, a prominent Black Lives Matter supporter, said those linking the attack to the movement don't have their facts straight.
"It goes without saying that the actions being branded by the far-right as the 'BLM Kidnapping' have nothing to do w/ the movement," he tweeted.
A former Chicago police officer, Dimitri Roberts, slammed the notion that the Black Lives Matter movement is to blame.
"This is hate. And hate doesn't have a color," Roberts said. "So for folks to talk about this is somehow connected to Black Lives Matter is absolutely the wrong way to look at this. ... And we cannot respond to hate with hate. It's just going to perpetuate the cycle."
President Barack Obama said the Facebook live torture video is "despicable," suggesting to CNN affiliate WBBM
it was a hate crime.
"What we have seen as surfacing, I think, are a lot of problems that have been there a long time," said Obama, a longtime resident of Chicago. "Whether it's tensions between police and communities, hate crimes of the despicable sort that has just now recently surfaced on Facebook."
"The good news is that the next generation that's coming behind us ... have smarter, better, more thoughtful attitudes about race," Obama said.
What constitutes a hate crime
According to the city of Chicago's website
, "Hate crimes are acts of bigotry, and are committed because of the intended victim's actual or perceived ancestry, color, creed, gender, race, religion, sexual orientation, physical or mental disability (including HIV status), or national origin. Hate crimes not only harm the victim, but also the group in which the targeted member belongs."
And according to Illinois law, hate can be considered an aggravating factor in a criminal charge and can result in a more severe sentence.
The assailants made a wide array of statements in the video, including repeated references to Donald Trump, white people in general and the victim's appearance.
How the encounter started
The victim's parents reported him missing Monday, telling police they had not heard from their son since dropping him off Saturday at a McDonald's in the Chicago suburb of Schaumburg, about 20 miles from their home in Crystal Lake.
The victim was supposed to spend New Year's Eve with Hill, who picked the teen up in a stolen van, Duffin said.
Hill drove the teen around for several days in the van -- they apparently spent at least one night in the vehicle -- before they went to the Covingtons' apartment in Chicago. Police said Hill and the teen were acquaintances who knew each other from school.
At one point, Hill and the teen got into a play fight that escalated and he was tied up for hours, police said.
A resident in another apartment complained about the noise and the two sisters went to the home and kicked down the door. The neighbor called 911.
Police responding to the call found the teen on the street wearing an inside-out tank top, shorts and sandals.
"He was bloodied, he was battered," Officer Michael Donnelly said. "He was very discombobulated."
Police in Streamwood, which borders Schaumburg, said that after the man was reported missing to them, his parents began getting text messages from someone "claiming to be holding him captive."
Officers investigating the texts "discovered a Facebook video depicting (the man) being verbally and physically abused." It's unclear what alerted the police to check Facebook.
Soon after they discovered the video, Streamwood investigators said they were contacted by Chicago police, who said they had found the missing teen.
After viewing the Facebook video, they determined the victim was the teen found on the street -- and the people arrested were involved, police said.
Video pulled from Facebook
Facebook said it pulled the original video from a suspect's Facebook profile.
"We do not allow people to celebrate or glorify crimes on Facebook and have removed the original video for this reason. In many instances, though, when people share this type of content, they are doing so to condemn violence or raise awareness about it. In that case, the video would be allowed."
According to its community standards
, the company removes content, disables accounts and works with law enforcement in cases of a genuine risk of physical harm or direct threats to public safety.
Facebook users also can report offensive material to the social platform. If a live stream starts blowing up, Facebook staffers monitor it for possible violations and interrupt it if needed.