It's worth stating what's probably obvious here which is that whatever happened here probably happened really fast and unexpectedly. So it's not surprising that the initial reports might be fragmentary or incorrect. But again, we have a very weird set of circumstances. I was at the dentist for the better part of the afternoon. So I'm only piecing together the details now. From the conflicting accounts, it seems that multiple law enforcement agents - at least one FBI agent and two Massachusetts police officers - were questioning this man in his home. So this wasn't in a police station or in an interrogation room. It seems that they were on the deceased man's turf.
Most reports suggest that the suspect had hinted at some involvement in the triple murder and then attacked the FBI agent with a knife once he was pressed for more details.
An account from ABC says this ...
The man shot dead by an FBI agent in Orlando, Florida early today was "about to sign a statement" admitting to a role, along with Boston Marathon bombing suspect Tamerlan Tsarnaev, in an unsolved triple murder in Massachusetts in 2011, two people with direct knowledge of the case told ABC News.
I would have to imagine that when you've got three law enforcement officers and one suspect, things have to spiral out of control really quickly before the suspect gets shot at point blank range. It also seems at least a little surprising to me that the officers wouldn't have secured the area they were questioning the man in or made sure he didn't have immediate access to a weapon, especially once (if the reports are correct) he admitted to a role in the killings. But I don't know what the procedures are or just how the events transpired. Presumably we'll have a clearer account of what happened soon.