The following editorial appeared recently in The Washington Post.

Last week, a team of FBI agents and Massachusetts police officers questioned Ibragim Todashev, an associate of Tamerlan Tsarnaev, a suspect in the Boston Marathon bombings who was killed days after that calamity.

One of the agents left the interview with minor injuries. Mr. Todashev was carted out with, apparently, several bullet holes in his body. We say "apparently" because journalists have gotten a tangle of conflicting reports from law enforcement sources about what happened.

As best we can make out, Mr. Todashev had confessed to participating with Mr. Tsarnaev, a fellow Chechen, in a 2011 triple murder. He then apparently did something to provoke an FBI agent in the room, and the agent shot him. An early account - all have been provided anonymously - indicated that Mr. Todashev had a knife. On Wednesday, though, it emerged that he was unarmed. Many reports agree that he overturned a table. Some suggest that Mr. Todashev might have been lunging for the agent's gun, or - weirdly - a samurai sword in the room. The Washington Post reported that the agent may have been alone with Mr. Todashev at the time of the scuffle.

From Moscow, Mr. Todashev's father is alleging that the FBI executed his son. With the eyes of the world once again on the United States' response to an act of terrorism and its treatment of foreign nationals, the last thing the U.S. government needs to do is fuel wild conspiracy theories by releasing too little information or investigating too slowly.

Even if the world weren't watching, the case would warrant exceptional attention. Mr. Todashev had had run-ins with law enforcement before last week, and his possible involvement in a gruesome triple murder is chilling. FBI agents may very well have had reason to worry about him. But if so, did they really leave a samurai sword in the room? Did they really leave only one person with Mr. Todashev? If neither of those accounts holds up, how else could the shooting be justified?

The FBI said that it takes the incident "very seriously," that it is reviewing the events internally with its "time-tested" procedures and that it is doing so "expeditiously."

The curious circumstances suggest that standard procedure might not be sufficient.