Just how firm the man's alleged connection to the marathon case is, though, remains unclear.
The dead man has been identified by NBC, the Orlando Sentinel and Orlando's WESH-TV as 27-year-old Ibragim Todashev. Another man, Khusn Taramiv, was the first to connect Todashev's death to the investigation into the Aprill 15 bombings in Boston. The Sentinel says that:
"Taramiv told several television outlets his friend was being investigated as part of the Boston bombings and Todashev knew bombing suspect Tamerlan Tsarnaev because both were mixed martial-arts fighters."
A source with knowledge of what happened tells our colleagues that the FBI agent was conducting an interview related to the bombings investigation when the individual being questioned became violent. Other law enforcement personnel were there, as well. During the confrontation, the source tells the NPR correspondents, "the individual was killed."
So far, according to the Sentinel, FBI spokesman Dave Couvertier has only officially confirmed that "the agent encountered the suspect while conducting official duties. ... We are still gathering facts involving the shooting incident."
Taramiv, the friend of the suspect killed in Orlando, has told WESH-TV that "(the FBI) took me and my friend (Ibragim Todashev). They were talking to us, both of us, right? And they said they need him for a little more, for a couple more hours, and I left, and they told me they're going to bring him back. They never brought him back."
Taramiv also said Todashev, like Boston suspect Tsarnaev, was an ethnic Chechen and that the two men spoke to each other by telephone a month or so before the marathon bombings. "He wasn't radical," Taramiv said of his friend, Todashev.
Tsarnaev, 26, died on April 19 from injuries he sustained during a gun battle with police in Watertown, Mass. The other suspect in the bombings, his 19-yer-old brother Dzhokhar, was captured on April 19. He has been charged with using a weapon of mass destruction.
Update at 10:50 a.m. ET. More On What Happened.
Here's how NPR's Dina Temple-Raston described what happened to our Newscast Desk:
"It all happened shortly in the small hours of this morning. An FBI agent and a handful of law enforcement officials went to the Orlando apartment of Ibragim Todashev to interview him, when a scuffle broke out.
"Law enforcement officials say Todashev was a friend of one of the Boston Marathon bombers, Tamerlan Tsarnaev. He became, in their words, violent, during questioning and that led to the fatal shooting.
"An FBI agent is in a local hospital with non-life threatening injuries.
"It is unclear why officials wanted to talk to Todashev."