A Maryland bioweapons scientist who was about to be indicted in the 2001 anthrax attacks has committed suicide.

A federal grand jury was preparing to indict a Maryland bioweapons expert for his role in the 2001 anthrax attacks that killed five people and terrorized the country, according to two sources familiar with the investigation.

Prosecutors were considering whether to seek the death penalty against Bruce E. Ivins, 62, who worked at an elite U.S. Army bioweapons laboratory in Fort Detrick. Ivins died Tuesday in an apparent suicide.

Paul F. Kemp, a criminal defense lawyer in Bethesda who has represented Ivins for the past year, declined to comment today but issued a statement that confirmed the federal investigation. He also asserted Ivins’ innocence.

“For more than a year, we have been privileged to represent Dr. Bruce Ivins during the investigation of the anthrax deaths of September and October of 2001,” Kemp said. “We assert his innocence in these killings, and would have established that at trial.”