(CNN) -- Deceased Boston Marathon bombing suspect Tamerlan Tsarnaev participated in a 2011 gruesome triple homicide outside Boston along with a Chechen killed early Wednesday during a confrontation with the FBI and Massachusetts State Police in Orlando, Florida, a federal law enforcement official told CNN.
Ibragim Todashev, who died during the interview with authorities, not only confessed to his direct role in slashing the throats of three people in Waltham, Massachusetts, but also fingered Tsarnaev in the deaths, the official said Wednesday.
Todashev was being questioned about the slayings and his acquaintance with Tsarnaev.
Todashev attacked an FBI agent, who shot him dead, a federal law enforcement official with direct knowledge of the case told CNN.
"He used some kind of weapon," the official said, and that prompted the FBI agent to shoot the suspect.
A second law enforcement official confirmed Todashev made the confession.
The unsolved triple murder received renewed interest after it was learned that Tsarnaev was sparring partners at a local gym with one of the victims.
Investigators of the crime reported at the time that the heads of the three victims were pulled back and their throats slit ear to ear with great force. Marijuana was spread over the bodies in a "symbolic gesture," and several thousand dollars in cash was found at the scene.
Todashev told investigators the men were killed during a drug ripoff because he and Tsarnaev were afraid they would be able to identify them and tell police what happened, according to a law enforcement source.
So far, no link has been found between Todashev and the Boston Marathon bombings. However, the FBI is looking into the many connections between Todashev and Tsarnaev, whose radicalization allegedly led to the Boston bombings.
A federal law enforcement official has told CNN they were initially led to Todashev because they learned he knew Tsarnaev and his younger brother, Dzhokhar. They also said cell phone records connected Tamerlan and Todashev.
Todashev was being interviewed in the kitchen of his Florida home. He grabbed a knife, which is why fatal force was used, according to a source briefed on the ongoing investigation.
"Preliminary information indicates the agent took actions to defend himself," said a federal law enforcement official with direct knowledge of the case.
"The agent sustained non-life-threatening injuries," FBI spokesman Jason Pack said.
Investigators are awaiting test results to determine whether Todashev's DNA was found at the Massachusetts triple murder scene and whether the DNA of Tamerlan Tsarnaev also was found there.
Todashev and Tsarnaev were acquainted through a mixed martial arts center near Boston, said a source briefed on the bombing investigation.
In Orlando, an FBI team is reviewing the circumstances of the shooting, a procedure that follows any FBI shooting.
Todashev had an impending flight from Orlando, via New York and Moscow, to Chechnya, when investigators sought to interview him, according to a source briefed on the ongoing investigation. He was told not to take the flight, the source said.
Details emerged Wednesday about how Todashev had Tsarnaev's phone number in his cell phone, said the source.
Both men were members of the mixed martial arts forum Sherdog.com, along with Russian-Canadian boxer-turned-jihadist William Plotnikov, the source said.
Last month, CNN reported that Plotnikov and six others died in a July 2012 firefight with Russian forces in the southwestern republic of Dagestan, while Tsarnaev was visiting the region, according to a source briefed on the investigation.
Todashev, 27, knew Dzhokhar Tsarnaev, also a suspect in the April 15 bombings, the official said. Dzhokhar Tsarnaev, injured and captured after a manhunt, is being held by authorities. His brother died in a shootout with police.
Todashev was from the Chechnya region, as were the Tsarnaev brothers, the source said.
Todashev was granted political asylum in 2008, but he came to the United States some time before that, a federal law enforcement official told CNN. Todashev had been living in the United States as a legal resident because of that asylum claim.
In the 2011 Massachusetts triple homicide, the Middlesex County district attorney's office said at the time that the victims and two unknown perpetrators appeared to know each other and that it was not a random crime. No suspects were named then.
A source said that the FBI had been investigating Todashev for about a month.
The FBI had followed Todashev for days, his friend told CNN affiliate Central Florida News 13.
Todashev "wasn't like real close friends (with Tsarnaev), but he just happened to know him," Khasuen Taramov told the TV station. "But he had no idea that they were up to something like that, like bombings and everything, you know what I mean?"
He told CNN affiliate WESH that Todashev and Tsarnaev had spoken by telephone about a month before the bombings.
"It was a complete shock to him," Taramov said.
The two met a couple years ago in Boston, where Todashev had lived and where there is a small, close-knit community of Chechens, said Taramov.
Their telephone conversation before the bombings contained nothing but routine pleasantries, he said. "It was 'How are you doing; how's your family?' That's all."
Taramov said he himself was questioned by the FBI for three hours Tuesday night. Asked what he was asked, Taramov said, "Different kind of questions like 'what do you think about bombings,' 'do you know these guys,' blah blah blah, what is my views on certain stuff."
He said Todashev was not a radical. "He was just a Muslim. That was his mistake, I guess."
Taramov said his friend had told him he had a bad feeling about the direction the investigation was heading.
"He felt like there's going to be a setup ... bad setup against him. Because he told me, 'They are making up such crazy stuff, I don't know ... why they doing it. OK, I'm answering the questions, but they are still making up some, like, connections, some crazy stuff. I don't know why they are doing it.' "
Before meeting with the FBI for a 7:30 p.m. interview Tuesday, Taramov said, his friend asked him to take his parents' telephone numbers. "He just told me, 'Take the numbers, in case something happens, if I get locked up, or whatever, call them.' You know what I mean?
"We were expecting to get him locked up, but not getting him killed. I can't believe it."
Todashev was unemployed and had been living on insurance money he received after surgery for an accident. "He used to be a fighter, MMA fighter," Taramov said, in a reference to mixed martial arts.
Todashev was arrested this month on a charge of aggravated battery after getting into a fight over a parking spot with a man and his son outside an Orlando mall. The son was taken to a hospital with head injuries, a split upper lip and several teeth knocked out of place, the Orange County Sheriff's Office said in a report.
"Todashev said he was only fighting to protect his knee because he had surgery in March," the report said. He told the police that he was a former mixed martial arts fighter, it said.
Todashev, described as 5-foot-9 and 160 pounds, was released on $3,500 bond.
Asked about the incident, Taramov downplayed it. "He had a fight in the parking lot, the two guys jumped on him ... pretty much he just defended himself against two," he told WESH. "The only mistake: he did kick their ass and left."
Todashev had recently gotten his green card and had been planning to visit his parents in Chechnya and then return to the United States, but canceled the plans, Taramov said.
Now, he added, he was planning to call his friend's parents.
CNN's Michael Martinez, Jason Hanna and MaryLynn Ryan contributed to this report.