The 2001 anthrax attacks in the United States, also known as Amerithrax from its Federal Bureau of Investigation (FBI) case name, occurred over the course of several weeks beginning on Tuesday, September 18, 2001, one week after the September 11 attacks. Letters containing anthrax spores were mailed to several news media offices and two Democratic U.S. Senators, killing five people and infecting 17 others. According to the FBI, the ensuing investigation became "one of the largest and most complex in the history of law enforcement".
A major focus in the early years of the investigation was a bio-weapons expert named Steven Hatfill, who was eventually exonerated. Another suspect, Bruce Edwards Ivins, became a focus of investigation around April 4, 2005. Ivins was a scientist who worked at the government's biodefense labs at Fort Detrick in Frederick, Maryland. On April 11, 2007, Ivins was put under periodic surveillance and an FBI document stated that "Bruce Edwards Ivins is an extremely sensitive suspect in the 2001 anthrax attacks". On July 27, 2008, Ivins killed himself with an overdose of acetaminophen.