Attack: Sept. 18, 2001
The first anonymous letters containing anthrax spores are mailed to assorted congressional and media targets, including Tom Brokaw and Sen. Tom Daschle. Over the next two months, anthrax inhalation kills five people and infects 17 others.
Breakthrough: July 26, 2008
Clues in the case prove difficult to pin down. Soon after the FBI searched Army microbiologist Bruce Ivins’ home, Ivins kills himself. A case against him could never go to trial.
Closure: Feb. 19, 2010
The FBI concludes Ivins acted alone and closes the case after more than eight years of controversy, false leads, and investigations of more than 1000 people. The Department of Justice later disputes Ivins’ involvement in 2011 and the investigation continues to be contended.