Updated 7:45 a.m., May 23

An FBI agent shot and killed an Orlando man and former mixed-martial arts fighter believed to be tied to Tamerlan Tsarnaev, the deceased Boston Marathon bombing suspect.

Early this morning, during a post-midnight interview with Ibragim Todashev at his apartment, an FBI agent shot Todashev. An interview with Todashev about his connections to Tsarnaev began peacefully, with Todashev reportedly cooperating, before taking a fatal turn for unclear reasons.

"There was some sort of aggressive movement that led the FBI agent to believe he was under threat and he opened fire," an anonymous law-enforcement official told ABC News.

An initial inquiry to the FBI about what happened in Orlando last night has yet to be answered; this post will be updated when more information is available.

A friend of Todashev's who says he was also interviewed by the FBI, Khusn Taramiv, said Todashev was a friendly acquaintance of the elder Tsarnaev brother from Boston. Both are of Chechen origin, but did not meet in Chechnya, Taramiv told the local NBC affiliate WESH-TV.

According to Taramiv, Todashev knew Tsarnaev from the tight-knit community of Chechens in Boston. Todashev spoke with Tsarnaev about a month before the bombings, possibly on Skype, after noticing him online; Tamerlan Tsarnaev's name was in Todashev's phone. Taramiv said that Todashev didn't know anything about the bombings and wasn't any sort of extremist. Todashev apparently got his green card recently and was planning a trip to Chechnya to see his parents. According to Taramiv, Todashev never owned a weapon and worried that the FBI was trying to set him up in connection to the bombings.

Todashev was also arrested recently in what Taramiv described as a parking lot altercation with two men who jumped him. A former mixed-martial arts fighter, there are a number of YouTube videos purporting to show his fighting career, and this MMA website lists him recording a win in a single bout. (Tamerlan Tsarnaev was a boxer in Massachusetts.)

One of the biggest questions surrounding the Boston bombings case is whether the Tsarnaev brothers, the alleged perpetrators of the April bombings that killed three people and wounded over 260 more, acted alone. While Taramiv says Todashev was unconnected to the attack, he said the FBI had been trailing them for at least a week. Dzhokhar Tsarnaev, the surviving Boston bombing suspect, is believed to have cooperated with investigators after sustaining serious bullet wounds prior to his arrest last month. Earlier this month, Boston law enforcement also arrested three of Dzhokhar Tsarnaev's college friends.

Update, 11:23 a.m.: The FBI says in a statement that the agent in question "sustained non-life threatening injuries" at Todashev's hands:

The FBI is currently reviewing a shooting incident involving an FBI special agent. Based on preliminary information, the incident occurred in Orlando, Florida during the early morning hours of May 22, 2013. The agent, 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. During the confrontation, the individual was killed and the agent sustained non-life threatening injuries. As this incident is under review, we have no further details at this time.

According to NBC, Todashev came at the agent with a knife; and "confess[ed]" to playing an unspecified role in a 2011 triple murder in Massachusetts that involved sprinkling marijuana on the corpses of three men with slit throats. He apparently wasn't suspected of involvement in the Boston bombings.

Update, 7:45 a.m., May 23: The FBI's Shooting Incident Review Team is on the scene in Orlando now, confirms spokesman Dave Couvertier. The team arrived in Orlando yesterday morning. "We cannot comment any further at this time," Couverterier says.