A heavily armed gunman opened fire at a movie theater in Aurora, Colorado, on Friday, July 20, killing at least 12 and wounding 38. Police arrested a suspect in theater's parking lot.
Here are some of the worst U.S. mass shootings since World War II.
November 5, 2009 -- Maj. Nidal Malik Hasan, 39, allegedly kills 13 people and injures 32 at Fort Hood, Texas, during a shooting rampage. He is charged with 13 counts of pre-meditated murder and 32 counts of attempted murder, and is awaiting trial.
April 3, 2009 -- In Binghamton, New York, Jiverly, 41, Wong kills 13 people and injures four during a shooting at an immigrant community center. He then kills himself.
March 10, 2009 -- In Alabama, 28-year-old Michael McLendon of Kinston kills 10 and himself. The dead include his mother, grandparents, aunt and uncle.
April 16, 2007 -- On the Virginia Tech campus in Blacksburg, 23-year-old student Seung-Hui Cho goes on a shooting spree, killing 32 people in two locations and wounds an undetermined number of others. He then commits suicide.
April 20, 1999 -- Two students, Dylan Klebold, 17, and Eric Harris, 18, carrying guns and bombs, open fire inside Columbine High School in Littleton, Colorado. They kill 13 and wound 23 others before killing themselves.
October 16, 1991 -- In Killeen, Texas, 35-year-old George Hennard crashes his pickup through the wall of a Luby's Cafeteria. Hennard shoots and kills 23 people before committing suicide.
July 18, 1984 -- In San Ysidro, California, 41-year-old James Huberty shoots and kills 21 adults and children at a local McDonald's. A police sharpshooter kills Huberty an hour after the rampage begins.
September 25, 1982 -- In Wilkes-Barre, Pennsylvania, 40-year-old prison guard George Banks kills 13 people, including five of his children. His death sentence is overturned in 2010.
August 1, 1966 -- At the University of Texas in Austin, Charles Joseph Whitman, 25, kills 16 and wounds at least 30 from a university tower. Police officers shoot and kill Whitman in the tower. Whitman also killed his mother and wife earlier in the day.
September 5, 1949 -- In Camden, New Jersey, 28-year-old Howard Unruh, a veteran of World War II, shoots and kills 13 of his neighbors. He is found insane and is committed to a state mental institution.