A Chechen man who was fatally shot by an FBI agent a week ago during an interview about one of the Boston bombing suspects was unarmed, law enforcement officials said Wednesday.

An air of mystery has surrounded the FBI shooting of Ibragim Todashev, 27, since he was killed in his apartment early on the morning of May 22. The FBI said in a news release that day that Todashev, a former Boston resident who knew bombing suspect Tamerlan Tsarnaev, was killed during an interview with several law enforcement officers.

But the bureau has provided few other details, saying that the matter is being investigated by an internal review team that may not finish its probe for several months.