The ensuing investigation by the FBI and its partners—code-named “Amerithrax”—has been one of the largest and most complex in the history of law enforcement.

In August 2008, Department of Justice and FBI officials announced a breakthrough in the case and released documents and information showing that charges were about to be brought against Dr. Bruce Ivins, who took his own life before those charges could be filed. On February 19, 2010, the Justice Department, the FBI, and the U.S. Postal Inspection Service formally concluded the investigation into the 2001 anthrax attacks and issued an Investigative Summary.

The Amerithrax Task Force—which consisted of roughly 25 to 30 full-time investigators from the FBI, the U.S. Postal Inspection Service, and other law enforcement agencies, as well as federal prosecutors from the District of Columbia and the Justice Department’s Counterterrorism Section—expended hundreds of thousands of investigator work hours on this case. Their efforts involved more than 10,000 witness interviews on six different continents, the execution of 80 searches, and the recovery of more than 6,000 items of potential evidence during the course of the investigation.

The case involved the issuance of more than 5,750 grand jury subpoenas and the collection of 5,730 environmental samples from 60 site locations. In addition, new scientific methods were developed that ultimately led to the break in the case—methods that could have a far-reaching impact on future investigations.