WASHINGTON AP – An Army scientist committed suicide as federal prosecutors readied an indictment alleging he mailed anthrax-laced letters in 2001 in what authorities said Friday may have been a bizarre attempt to test a vaccine for the deadly poison.

The scientist, Bruce E. Ivins, worked at the Army’s biodefense labs at Ft. Detrick, Md., for 18 years until his death on Tuesday. He had a long history of homicidal threats, according to papers recently filed in local court by a social worker.