How America has been rocked by attack after attack
Below are some of the worst shooting incidents in recent years, ranked by the number of dead, including the gunman:
April 16, 2007 - A gunman slaughters 32 people and kills himself at Virginia Tech, a university in Blacksburg, Virginia.
Dec 14, 2012 - A gunman kills 20 children, six adults and himself at Sandy Hook Elementary School in Newtown, Connecticut.
April 20, 1999 - Two heavily armed teenagers go on a rampage at Columbine High School in Littleton, Colorado, shooting 12 students and a teacher to death and wounding more than 20 others before taking their own lives.
April 3, 2009 - A Vietnamese immigrant opens fire at an immigrant services centre in Binghamton, New York, killing 13 people and wounding four. He then kills himself.
Nov 5, 2009 - A gunman opens fire at Fort Hood, a US Army base in Texas, killing 13 people and wounding 32. The gunman, an Army major and psychiatrist, was sentenced to death for the rampage.
Washington Navy Yard
Sept 16, 2013 - A former Navy reservist working as a government contractor kills 12 people at the Washington Navy Yard. Eight people are injured. The gunman was killed by police.
Colorado movie theatre
July 20, 2012 - A masked gunman kills 12 people and wounds 70 when he opens fire on moviegoers at a midnight premiere of the Batman film The Dark Knight Rises in Aurora, a Denver suburb. A former graduate student is sentenced to life in prison for the rampage.
Washington DC snipers
October 2002 - Two men ambush 13 people, killing 10 of them, in a string of sniper-style shootings that terrorise the Washington area.
Oct 1, 2015 - A gunman bursts into Umpqua Community College in southwest Oregon and opens fire, instantly killing nine people and wounding seven others before armed police shoot him to death.
June 17, 2015 - A white supremacist gunman kills nine black churchgoers during a Bible study session at a historic, predominantly black church in Charleston, South Carolina. The suspect is awaiting trial.
May 17, 2015 - Rival motorcycle gangs kill nine at a restaurant in Waco, Texas. More than 170 are arrested.
Grandfather kills family
Sept 18, 2014 - A man kills his daughter and six of his grandchildren in Bell, Florida, before turning the weapon on himself.
April 2, 2012 - A former student kills seven students at Oikos University, a small Christian school in Oakland, California. The suspect is awaiting trial.
Aug 5, 2012 - A white supremacist walks into a Sikh temple in Oak Creek, Wisconsin, shoots six worshippers and wounds four others, including a policeman. The gunman kills himself after being shot by a police officer.
July 26, 2013 - A man goes on a shooting spree at an apartment complex in Hialeah, Florida, killing six people. The shooter is killed by police.
Congresswoman assassination attempt
Jan 8, 2011 - Then US Representative Gabrielle Giffords is the target of an assassination attempt by a gunman in Tucson, Arizona, in which six people are killed and 13, including Giffords, are wounded.
Nov 27, 2015 - A gunman storms a Planned Parenthood health clinic in Colorado Springs, Colorado, killing three people and wounding nine. Police arrest the gunman.
Aug 26, 2015 - A reporter, Alison Parker, and a cameraman, Adam Ward, are killed during a live broadcast by suspected gunman Vester Lee Flanagan, who posted his own video of the shooting before killing himself. Flanagan was a former employee of their Roanoke, Virginia, television station while the two victimes were interviewing a woman on live TV. The woman was wounded but survived.