Using numbers from the Centers for Disease Control and Prevention, we found that from 2001 to 2013, 406,496 people died by firearms on U.S. soil. (2013 is the most recent year CDC data for deaths by firearms is available.) This data covered all manners of death, including homicide, accident and suicide.
According to the U.S. State Department, the number of U.S. citizens killed overseas as a result of incidents of terrorism from 2001 to 2013 was 350.
In addition, we compiled all terrorism incidents inside the U.S. and found that between 2001 and 2013, there were 3,030 people killed in domestic acts of terrorism.* This brings the total to 3,380.
*Includes the following domestic terrorism incidents:
September 11 attacks (NY, DC, PA) 9/11/01
2001 Anthrax attacks (DC, NY, CT, FL) Oct., Nov. 2001
El Al counter shooting (California) 7/4/02
Beltway sniper attacks (DC, Mid-Atlantic) Oct. 2002
Knoxville church shooting (Tennessee) 7/27/08
Pittsburgh police officers killed (Pennsylvania) 4/4/09
Tiller abortion clinic (Kansas) 5/31/09
Holocaust Museum shooting (DC) 6/10/09
Fort Hood shooting (Texas) 11/5/09
Plane crash into Austin IRS building (Texas) 2/18/10
Fort Stewart Army base killing (Georgia) 12/10/11
Sikh Temple Shooting (Wisconsin) 8/7/12
St. John's Parish police ambush (Louisiana) 8/16/12
Boston Marathon Bombing (Massachusetts) 4/15/13
LAX Shooting (California) 11/05/13