Is this letter a coincidence, is there something more to it?
"On October 2, 2001 (three days before the first fatality from anthrax in the 2001 domestic US terrorism attacks), FBI Agent Gregory Leylegian called and asked Dr. Ayaad Assaad to come in for questioning, which he did the next day. The FBI had received an anonymous letter, postmarked September 21, 2001, in which an alleged co-worker warned that Dr. Assaad might be planning a biological attack. The timing is noteworthy because anthrax-victim Robert Stevens was not admitted to a Florida hospital until October 2nd, and he was not diagnosed with anthrax until October 3rd. The first set of letters containing real anthrax were mailed on September 18th.
The 212-word letter sent to the FBI was unsigned and computer-typed. It stated, in part: "Dr. Assaad is a potential biological terrorist. ... I have worked with Dr. Assaad and I heard him say that he has a vendetta against the U.S. government and that if anything happens to him, he told his sons to carry on." According to Assaad: "The letter-writer clearly knew my entire background, my training in both chemical and biological agents, my security clearance, what floor where I work now, that I have two sons, what train I take to work, and where I live."
http://en.wikipedia.org/wiki/Ayaad_Assaad