An FBI agent has shot and killed a Florida man who "turned violent" while being questioned about the Boston Marathon bombings, the bureau has said.
A friend of the dead man told the Orlando Sentinel and Orlando television stations that he was 27-year-old Ibragim Todashev of Orlando, a Chechen who had previously lived in Boston.
Two brothers identified by the FBI as suspects in the April 15 bombings were also of Chechen origin.
The FBI said in a statement that a special agent, "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".
It said the shooting occurred in Orlando, Florida, while the special agent and other law enforcement agents were interviewing the man about the blasts that killed three people and injured 264 others at the finish line of the Boston Marathon.
"A violent confrontation was initiated by the individual," the FBI said, without providing further details.
Todashev's friend, Khusn Taramiv, said Todashev knew bombing suspect Tamerlan Tsarnaev because both were mixed martial-arts fighters, but had no connection to the bombing.
"Back when he used to live in Boston, right, they used to hang out," Taramiv told Central Florida News 13.
"He met them few times 'cause he was MMA fighter the other guy was boxer, right. They just knew each other that's it," he said.
The shooting occurred at an Orlando apartment complex where several people of Chechen descent lived. Taramiv said Todashev and others in the complex had been questioned several times by law enforcement agents since the day the Tsarnaev brothers were identified as the bombing suspects.
Tamerlan Tsarnaev, 26, died in a gunfight with police. His brother, Dzhokhar Tsarnaev, 19, was found hiding in a boat in Watertown, Massachusetts, four days after the bombings. He was charged with crimes that could carry the death penalty if he is convicted.
Tamerlan Tsarnaev had been on a US government database of potential terrorism suspects and the United States had twice been warned by Russia that he might be an Islamic militant, according to US security officials.
In Florida, the Orange County Sheriff's Office said Todashev had been arrested on May 4 and charged with aggravated battery with great bodily harm. Details about the circumstances of the arrest were not immediately available.