Claim No. 1: He had a knife.

Where it came from: NBC News was one of the first outlets to turn the tide of the story — that Todashev drew a knife on investigators and that, after orally confessing to the triple murder but not yet finishing his written account, he got violent enough to get himself killed on the spot. The Associated Press attributed their own knife account to three anonymous law enforcement officials.

Is it true? We're not sure, but right now it looks unlikely. A couple of those three officials are now walking back their descriptions to the AP:

Three law enforcement officials, speaking on condition of anonymity, said Todashev had lunged at the FBI agent with a knife. However, two of those officials said later in the day it was no longer clear what had happened. The third official had not received any new information.

That's 66 percent of sources who are "no longer clear" if Todashev had a knife. The New York Times has one of its two senior law enforcement officials claiming Todashev had a knife "or a pipe or something." In CBS's report, there is no mention of the knife, but rather a violent "move" that Todashev made:

Law enforcement officials say the 27-year-old mixed martial arts fighter made a move that threatened the investigators.

And the FBI's official statement has no mention of a knife being drawn, but rather a "violent confrontation" which might be the "move" CBS is reporting:

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.

Why it matters: Well, one of the big questions is why the FBI used lethal force against Todashev. "This is something they should be trained for," Todashev's wife, Reni Manukyan, tells The Wall Street Journal today. "They should be trained to not use a gun in any way." If Todashev had a knife and charged at law enforcement officials, an argument could be made that lives were in danger. To be sure, he had a history: The Boston Globe describes Todashev as "a professional mixed martial arts fighter with a violent ­record."

But why shoot, when you've got a man with potential answers about the man behind a terror attack on American soil in front of you? "If somebody jumps on you and you have a gun, and you don’t do something, the gun will quickly come into play," one of the Times sources said. As NBC West Palm Beach reported, Todashev was meeting with FBI agents and two Massachusetts state troopers when he was shot. Outlets like New York's Daily News reported that Todashev "stabbed an FBI agent" before being shot — that would be harder to do without a knife.

As Gawker's Max Rivin-Nadler points out, investigators will have to figure out how Todashev, who was being interviewed at his house for three hours, came to be in possession of a knife (and if he actually did) and why a room full of law enforcement agents used lethal force against a man who might have been armed, at most, with a knife. Or something. And they'll have to deal with the fallout in a larger terror investigation and trial of Tsarnaev's younger brother.