A Chechen man linked to one of the Boston Marathon bombing suspects was fatally shot early Wednesday in an unusual encounter with the FBI and other law enforcement officers in his apartment in Orlando.

According to federal law enforcement officials, the man was being interviewed about whether he and Tamerlan Tsarnaev, the bombing suspect, were connected to a two-year-old triple slaying when he attacked an FBI agent. There were conflicting accounts of what happened in the moments before the man was shot.

One federal law enforcement official said the man, a professional martial-arts fighter, was shot after trying to grab the FBI agent’s gun. Two other officials said the man reached for a knife and was shot as he attacked the agent. All three officials spoke on the condition of anonymity because the episode is under official review.

The man was identified as Ibragim Todashev, 27, a former Boston area resident who knew Tsarnaev from martial-arts and boxing circles. Todashev had recently moved to Orlando from Cambridge, Mass.

Law enforcement officials said Todashev was not a suspect in the bombing. They said he was being interviewed about his possible role in a triple slaying in Waltham, Mass., in September 2011. They said Todashev acknowledged involvement in the killings and also implicated Tsarnaev in what the law enforcement officials described as a drug deal that went bad.

In this booking photo provided by the Orange County Sheriff's Office, Ibragim Todashev poses for his mug shot after being arrested on a charge of aggravated battery May 4 in Orlando. (Handout/Getty Images)

The FBI provided few details about the shooting in Orlando and did not mention the Waltham slayings, but the bizarre twist demonstrated the extent of the ongoing investigation into the April 15 Boston Marathon bombing, which killed three people and injured more than 260.

Dozens of FBI agents and other law enforcement officers have been conducting interviews across the United States and in Russia with associates of Tsarnaev and his brother, Dzhokhar, the other bombing suspect, to learn whether anyone else was associated with the Boston attack.

The interviews have focused largely on people from the northern Caucasus area of Russia, where Tamerlan Tsarnaev spent six months in 2012. The Tsarnaev family has roots in Chechnya, part of the restive region, and the FBI suspects that he might have had contact with Islamist militants there last year.

Reached Wednesday in the Russian republic of Dagestan, Anzor Tsarnaev, Tamerlan’s father, said that his son knew Todashev and that he believed the two had met while in the United States.

“All Chechens are like relatives,” the elder Tsarnaev said when told about the shooting in Florida. “This is all so sad.”

He questioned how Todashev could have been killed during an interrogation. “Why do they think they have the right to kill people?” he said. “It was a setup, like with Tamerlan.”

Tamerlan Tsarnaev was killed in a shootout with police four days after the bombing. His brother was captured later that day and faces charges that could carry the death penalty. Before he was charged, Dzhokhar Tsarnaev told the FBI that no one else was involved in the plot and that he and his brother had acted out of anger over the U.S. conflicts in Iraq and Afghanistan.

Shortly after midnight Wednesday, the FBI agent, two Massachusetts State Police officers and other law enforcement personnel went to Todashev’s apartment in a residential area near Universal Studios in Orlando to interview him about his relationship with Tsarnaev and their suspected ties to the Waltham slayings.

The law enforcement officials said he was initially cooperative and appeared to be on the verge of signing a confession when the interview turned into a confrontation. The FBI agent suffered minor injuries, and Todashev was fatally shot.

Todashev was arrested in early 2010 in Boston on charges including reckless driving. This month, he was arrested on a charge of aggravated battery after getting into a fight in an Orlando parking lot, according to police records. At the time of the Orlando arrest, he was driving a Mercedes with Georgia license plates.

Tsarnaev’s name had surfaced in earlier news reports about the Waltham slayings, which remain unsolved. Stephanie Guyotte, a spokeswoman for Middlesex County’s district attorney’s office, said the investigation is ongoing and refused to say whether Todashev or Tsarnaev was a suspect.

On Sept. 12, 2011, police found three men dead in a well-kept rental house on a short, quiet street in Waltham. The men were identified as Brendan Mess, 25, of Waltham, Erik Weissman, 31, of Cambridge and Raphael Teken, 37, of Cambridge. The Boston Globe and other news outlets have reported that Tsarnaev was friends with Mess and that the two met through boxing.

A woman who lived next door to the rental house said she was home that day and consoled Mess’s distraught girlfriend, who reportedly found the bodies and ran screaming outside. The neighbor, who spoke on the condition of anonymity because she does not want her name associated with the gruesome slayings, said she was told that the men had their throats slashed and that their bodies were covered with marijuana.

“She was horrified,” the neighbor said of the girlfriend. “We didn’t hear a thing that night. . . . The fact that all of this attention has come here again is very painful.”

Authorities say the men died early Sept. 12, but relatives of at least one of the victims insist that the men were killed Sept. 11, the 10th anniversary of the attacks in New York and at the Pentagon. Sept. 11 is the date listed on the tombstone of Weissman, according to photos posted on an online memorial.

At the time of the killings, Waltham police issued a statement saying that detectives did not think the attack was random and that the victims probably knew their attacker or attackers. The Middlesex district attorney’s office later said in a statement that the men died of “sharp-force injuries of the neck.’’

Two friends of Teken and Weissman said they believed the deaths were connected to a massive May 2011 drug bust in nearby Watertown. The bust followed a year-long investigation by federal authorities and resulted in charges against 18 people. Weissman was a founder of a company that produced glass bongs.

Julie Tate, Peter Finn and Peter Hermann in Washington and Natasha Abbakumova in Moscow contributed to this report.