After the service at the Mosque for the Praising of Allah, the place of worship of Rahim's family, his wooden casket was carried to a hearse and driven to the burial site. Several dozen people attended the service, including Rahim's immediate family.
Once he is buried, police will release the surveillance video of Rahim's shooting to the public, after holding it back per the family's request.
The family screened it Thursday, and it seemed to calm their initial suspicions about his death.
His brother, Ibrahim Rahim, originally posted to social media that police had killed Usaamah Rahim for no reason, shooting him in the back while he spoke on the phone with their father.
But after seeing the video, Ibrahim Rahim acknowledged that his initial post was not correct, and he asked the public not to jump to conclusions. But he still wanted to know more about his brother's death. "The facts are still coming in. We need more information," he told CNN's "Erin Burnett OutFront."
He said he had no indication his brother was hatching any kind of terror plan.
Community leaders who saw the images confirmed to the media much of what Boston police had said -- that FBI and police officers confronting Rahim on Tuesday initially did not have their guns drawn as he approached them.
The FBI says tapped phone conversations support its claim that Usaamah Rahim was going to carry out a knife attack against police at any moment, which is why the joint anti-terror team of federal and local officers confronted him when it did.
While the public awaits a chance to view the surveillance footage, investigators are working to fit together other pieces of the puzzle -- in particular how deep Rahim's support network was.
Did terror group ISIS enjoy more allegiance from him than just his "like" on Facebook? Did it have significant influence on him? His social media posts showed admiration for radical Islam, but were sparse and nonpolitical.
Or was his support limited to two associates who allegedly knew about and encouraged his alleged terror attack plan?
At least one of the men connected to the plot was being encouraged to launch an attack by people connected to ISIS
, who were communicating from overseas, two U.S. officials with knowledge of the investigation said. But they don't believe ISIS helped hatch a specific plan.
A law enforcement official said that interaction with ISIS included peer-to-peer communications, which are increasingly being used by jihadists and are more difficult to monitor.
Law enforcement officials said all three men were influenced by ISIS to some degree.
In 2012, Rahim posted on Facebook that he suspected the FBI had contacted him.
In a post under the alias Abdur-Rahim Al-Amreeki, Rahim apparently wrote: "Damn FBI calling my phone! ... He wanted to meet up with me and 'Talk.' HA! I said about WHAT? He said 'Sir, we have some allegations regarding you ...' I said 'REALLY?' What ALLEGATIONS? He said 'Well sir, that's what I wanted to meet up with you about. I came by your house a few times, but kept missing you.'"
The post continued: "I said, 'If you want to summon me, you summon that COURT ORDER if your allegations you claiming are true, otherwise, BEAT IT' and then I hung up."
A law enforcement official confirmed the Facebook page belonged to Rahim. The FBI has not commented on the post.
Counterterrorism officials have said they were monitoring Rahim for at least a couple of years.
Beheading target Geller
Authorities arrested David Wright, a man Rahim called his nephew, and whose conversations with Rahim the FBI recorded. Wright waved his Miranda rights before questioning, FBI agent Joseph Galietta said in an affidavit
Wright told Galietta that he and an associate from Rhode Island had talked with Rahim about an attack plan. And Wright had approved of it.
The Rhode Island associate has not been named. A law enforcement official told CNN that the man is a friend of Rahim and Wright.
An FBI affidavit said the unidentified man attended a May 31 meeting with Rahim and Wright on a beach in Rhode Island to discuss "their plans," including the idea of beheading controversial blogger Pamela Geller
Investigators have searched the man's home and questioned him but have not arrested or charged him, law enforcement officials said. His role remains under investigation and the police presence outside the Warwick, Rhode Island, home remains heavy three days after it was searched.
In March, a CNN producer exchanged messages with the man known only as the "third person" in the affidavit. A law enforcement officer confirmed the man's identity to CNN. The producer was doing research on Americans who identify with jihadists online.
During the conversation with CNN, the Rhode Island resident described exchanges with an alleged ISIS fighter who was trying to urge him to come to Iraq and Syria and join the group. He said he considered it.
An analysis of his Twitter feed indicates he actively reached out to individuals connected with ISIS, including Mujahid Miski, the online alias of Mohamed Abdullahi Hasan, a Minnesotan believed to be fighting with Al-Shabaab in Somalia.
Miski was in direct contact with Elton Simpson, one of the two shooters in the Texas attack on Geller's controversial "Draw Your Own Mohammed" event in May.
The Rhode Island resident told CNN in the online exchanges that he attended services at a mosque near his home but never shared his interpretation of Islam with his imam. He said he was agnostic, seeking "truth and guidance" before converting to Islam.
A court charged Wright with obstructing a federal investigation, after he allegedly destroyed evidence on Rahim's smartphone. He faces a maximum penalty of five years in prison.
Rahim had initially set his sights on an ISIS-style beheading, and his chosen victim, according to law enforcement officials, was conservative blogger Geller.
The high-profile Islam
critic organized a Prophet Mohammed cartoon drawing contest in Garland, Texas, last month
. Two men tried to shoot participants at that event, but an off-duty police officer working security shot them dead.
"They are coming after me for violating the Sharia, for violating blasphemy laws, and they mean to come after everyone," she said. "Drawing a cartoon, an innocuous cartoon, warrants chopping my head off? That's too far. I just don't understand this."
Since the Texas incident, Geller said, she has been guarded 24 hours a day.
'Boys in blue'
Rahim got impatient about his target, the FBI said, and focused on a much more accessible one: police officers.
"I'm just going to, ah, go after them, those boys in blue. Cause, ah, it's the easiest target," Rahim told Wright, in a telephone conversation that Galietta listened to.
Rahim referred to his plan to carry out violent jihad as "going on vacation." He said he'd be going soon, right where he was in Massachusetts, and Wright told him he should make out a will, the affidavit said.
The FBI had been keeping tabs on Rahim for a couple of years, and in the 10 days before his shooting, the agency watched him 24 hours a day, it said. Rahim ordered military-grade fighting knives online. Officers intercepted and X-rayed at least one delivery.
Said 'his goodbyes'
About two hours after the phone conversation with Wright, officers decided it was time to move.
Just before they arrived, Rahim called his father to say "his goodbyes," a law enforcement official said. Investigators heard the conversation.
They believed Rahim was going to board a public bus with his military knife. But the FBI and Boston police team approached him in a parking lot ahead of time.
Rahim pulled a knife and went after the officers, they said, and officers drew their weapons and shot him dead.