The suspect, identified as Ibragim Todashev, 27, was from Chechnya and had ties to slain Boston Marathon bombing suspect Tamerlan Tsarnaev, the FBI said in a statement Wednesday.
A former FBI agent who now works for a news organization told WKMG-TV, Orlando, the FBI was trying to re-question Todashev at his Orlando apartment when "something went wrong."
"The agent went along with two Massachusetts State Police troopers and other law enforcement personnel were interviewing an individual in connection with the Boston Marathon bombing investigation when a violent confrontation was initiated by the individual," the FBI statement said. "During the confrontation, the individual was killed and the agent sustained non-life threatening injuries."
The FBI declined to release details of the confrontation in a quiet neighborhood near Universal Studios saying only that the incident was under review.
Khusen Taramiv, a friend of Todashev, told WESH-TV, Orlando, both he and Todashev had been questioned about ties to Tamerlan Tsarnaev, whom they met when they both lived in Massachusetts.
He told television reporters the men did mixed martial arts fighting with Tamerlan Tsarnaev in Boston but, "they were not best friends" and Todashev was not involved in the Boston bombings.
He was not a radical. He was a Muslim," Taramiv said. "I'm a Muslim. That's it ... He ever had a gun ... He was shocked," by the bombings.
The Orlando Sentinel said Todashev had been arrested May 4 following a fight over a mall parking space and charged with aggravated battery with great bodily harm by the Orange County Sheriff's Office.
The men last spoke months before the April 15 bombing that killed three people and wounded more than 260 others, the Boston Globe said. Dzhokhar Tsarnaev, Tamerlan's younger brother, is in federal custody and faces capital charges in the bombing.
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