Yes, as U.S. attorney general John Ashcroft said, “When people send anthrax through the mail to hurt people and invoke terror, it’s a terrorist act.” Investigators believed the attacks, which killed 5 people and sickened 17 others, were acts of domestic terrorism. But whoever was responsible for mailing anthrax spores in the fall of 2001 remained unknown in mid-2005. Some observers believed the attacks were carried out to expose the nation’s vulnerability to bio-terrorist attacks.