The deadly school shooting at a Connecticut elementary school on Friday was the latest shooting crime in the United States this year. Below are some of the worst such incidents in recent years:
April 1999 - Two heavily armed teenagers go on a rampage at Columbine High School in Littleton, Colorado, shooting 13 students and staff before taking their own lives.
July 1999 - A gunman kills nine people at two brokerages in Atlanta, after apparently killing his wife and two children. He commits suicide five hours later.
October 2002 - Two men kill at least 10 people in a string of sniper-style shootings that terrorize the Washington, D.C., area.
November 21, 2004 - Six people are killed when a man shoots eight people while deer hunting in northern Wisconsin.
March 12, 2005 - A man opens fire at a Living Church of God service at the Sheraton Hotel in Brookfield, Wisconsin, killing seven and wounding four. He then commits suicide.
April 16, 2007 - A gunman kills 32 people and himself at Virginia Tech, a university in Blacksburg, Virginia.
October 7, 2007 - A sheriff's deputy kills six people and wounds one at his ex-girlfriend's apartment, in Crandon, Wisconsin. He then kills himself.
April 3, 2009 - A Vietnamese immigrant opens fire at an immigrant services center in Binghamton, New York, killing 13 people. He then kills himself.
November 5, 2009 - A gunman opens fire at Fort Hood, a U.S. Army base in Texas, killing 13 people and wounding 32. An Army major is charged in connection with the rampage.
January 8, 2011 - Then-U.S. Congresswomen Gabrielle Giffords is the target of an assassination attempt in Tucson, Arizona, in which six people are killed and 13, including Giffords, are wounded.
April 2, 2012 - A gunman kills seven people and wounds three in a shooting at a Christian college in Oakland, California.
July 20, 2012 - A masked gunman kills 12 people and wounds 58 when he opens fire on moviegoers at a showing of the Batman film "The Dark Knight Rises" in Aurora, a suburb of Denver. A 24-year-old former university student is charged in connection with the rampage.
August 5, 2012 - A gunman kills six people during Sunday services at a Sikh temple in Oak Creek, Wisconsin, before he is shot dead by police.
December 11, 2012 - A gunman opens fire inside an Oregon shopping mall, killing two people and wounding one. He then kills himself.
December 14, 2012 - A heavily armed gunman kills at least 20 children and six adults at an elementary school in Newtown, Connecticut, and a body is found elsewhere in the town. The gunman is also dead.