ORLANDO, Fla./WASHINGTON - A Chechen immigrant who was being questioned about his possible links to one of the Boston Marathon bombing suspects was shot and killed by a federal agent in Florida on Wednesday after he suddenly turned violent, the FBI said.

A friend of the dead man identified him to Reuters as 27-year-old Ibragim Todashev, who had previously lived in Boston and knew Tamerlan Tsarnaev, the older of the two brothers suspected of planting two bombs at the marathon on April 15, killing three people and injuring 264.

NBC News reported that Todashev had confessed to his involvement in an unsolved 2011 triple homicide in a Boston suburb that investigators believe was drug related, citing law enforcement officials.

Authorities were investigating possible connections between Tsarnaev, who died in a shootout with police, and the 2011 incident.

Three men including a close friend of Tsarnaev were found stabbed in the neck in an apartment on September 12, 2011, in Waltham, Massachusetts. News reports said marijuana was strewn over their bodies.

Wednesday's incident took place at an apartment complex near the Universal Studios theme park, where the FBI and members of other law enforcement agencies were interviewing the man about the marathon bombing.

"A violent confrontation was initiated by the individual," the FBI said. A special agent, it said, "acting on the imminent threat posed by the individual, responded with deadly force. The individual was killed and the special agent was transported to the hospital with non-life-threatening injuries."    

The possibility that Tsarnaev was connected to the Waltham murders is "being looked at seriously," said Republican Representative Peter King, who serves on the House Homeland Security Committee. Other US officials confirmed the investigation did involve Tsarnaev's possible role.

Tamerlan Tsarnaev, 26, and his 19-year-old brother Dzhokhar are suspected of setting off two pressure-cooker bombs at the marathon finish line. Dzhokhar is being held at a prison hospital west of Boston awaiting trial on charges that carry the possibility of the death penalty.

"NOTHING TO HIDE"

Todashev knew Tsarnaev because both were mixed martial-arts fighters in Boston but had no connection to the bombing, a friend of Todashev, Khusen Taramov, told Reuters in an interview.

Todashev was tailed by law enforcement agents since the day the Tsarnaev brothers were identified as suspects in the Boston bombing and called in for questioning repeatedly, he said.

"They called him a lot. They would just call and question him," Taramov said, adding he and his friend had met with FBI agents on several occasions.

Asked about the 2011 triple homicide he said it never came up in the meetings with the FBI that he personally attended. He said Taramov never mentioned the murders either.

"He had nothing to hide. Everything he knew, he told them," Taramov said.

Taramov said he met FBI agents on Tuesday night outside the apartment complex where his friend was killed but was told by the FBI to leave shortly before the shooting happened around midnight. He added that Todashev, who was in the United States as a legal permanent resident, had been planning a trip back to Russia where his parents live.

Law enforcement officials have also interviewed another person of Chechen origin, ex-rebel Musa Khadzhimuratov, at his home in New Hampshire, the New York Times reported last week.   Khadzhimuratov, who had served as a bodyguard to a top Chechen separatist leader during the region's civil war with Russia more than a decade ago, also had contact with Tsarnaev.

Neighbors said that in recent weeks, they had noticed what looked like undercover officers in unmarked cars in the parking lot outside the apartment complex where Todashev was shot and killed. Several neighbors said he jogged on the paths through the complex shadow boxing, and sometimes swam laps in the pool and sparred with friends on the pool deck.

Todashev was arrested on May 4 and charged with aggravated battery after getting into a fight with another man over a parking space at an Orlando shopping mall, according to the Orange County Sheriff's Office in Orlando.

The man, who suffered a split upper lip and had several teeth knocked out of place, did not to press charges against Todashev, who was released from jail on a $3,500 bond, a sheriff's spokeswoman said.

Before the Boston bombings, Tamerlan Tsarnaev had been listed on multiple US government databases, including a master list of potential terrorism suspects. US authorities also were asked twice by Russia to investigate Tsarnaev for possible involvement with Islamic militants, US officials have said.

Also, on Wednesday afternoon, US Attorney General Eric Holder was scheduled to meet in Washington with Vladimir Kolokoltsev, Russia's interior minister. The meeting's agenda was unclear, but US investigators are anxious to learn what Russian authorities knew about the Tsarnaevs and about what Tamerlan Tsarnaev did during a six-month trip to Russia last year.