The unsealing of hundreds of pages of material, including search warrants against the man FBI agents believed to be the sole culprit in the 2001 anthrax-by-mail attacks that killed five people, gave a clearer picture of Ivins' behavior, The Washington Post said Thursday.

"I finally know who mailed the anthrax letters in the fall of 2001. I should have been a private eye," Ivins said in a message sent last September.

After learning that FBI scientists had traced the bacteria to his laboratory, Ivins, a government bioweapons researcher, suggested to agents several other scientists who he said might be guilty, the documents say.

Ivings died July 29 after an overdose of Tylenol as prosecutors moved closer to charging him with the largest bioterrorism attack in U.S. history.