With the release of some Anthrax investigation documents by the FBI, it’s clear all the evidence against Bruce Ivins is circumstantial.

Federal investigators described the following key points against Ivins:

(1) At the time of the attacks, he was the custodian of a large flask of highly purified anthrax spores that possess certain genetic mutations identical to the anthrax used in the attacks;

(2) Ivins has been unable to give investigators an adequate explanation for his late night laboratory work hours around the time of both anthrax mailings;

(3) Ivins has claimed that he was suffering serious mental health issues in the months preceding the attacks, and told a coworker that he had “incredible paranoid, delusional thoughts at times” and feared that he might not be able to control his behavior;

(4) Ivins is believed to have submitted false samples of anthrax from his lab to the FBI for forensic analysis in order to mislead investigators;

(5) at the time of the attacks, Ivins was under pressure at work to assist a private company that had lost its FDA approval to produce an anthrax vaccine the Army needed for U.S. troops, and which Ivins believed was essential for the anthrax program at USAMRIID; and

(6) Ivins sent an email … a few days before the anthrax attacks warning that “Bin Laden terrorists for sure have anthrax and sarin gas” and have “just decreed death to all Jews and all Americans,” language similar to the anthrax letters warning “WE HAVE THIS ANTHRAX . . . DEATH TO AMERICA . . . DEATH TO ISRAEL.”

Given that the suspect is dead, we are left with just one side of the story; to some, like the NYT, that’s enough. But it’s hard not to be suspicious.

As many jump to question the absurd of having a paranoid, delusional working with bioweapons, conspiracy theories are abounding on the internet: it all seems too easy. The FBI claims to have a lot of evidence against him, but such evidence hasn’t been examined by anyone else.

Perhaps Bruce Ivins did it, alone, by himself, and took his reasons and explanations with him to the grave. Perhaps his suicide was bad luck for the FBI, that had been tracking him for years.

But equally possible is that the FBI had very little, pressed hard against the only suspect they had, the guy broke down, and now the federals need to use that to close the case and get it over with.