The mass shooting at a Connecticut elementary school on Friday is among the most deadly worldwide in recent years.
Here is a timeline of some of the worst shooting incidents carried out by one or two gunmen around the world in the past two decades.
April 1982 - SOUTH KOREA - A police officer went on a drunken rampage in Sang-Namdo with rifles and hand grenades, killing 57 people and wounding 38 before blowing himself up.
August 19, 1987 - BRITAIN - A 27-year-old gunman rampaged through the English town of Hungerford, killing 16 people and wounding 11 before shooting himself.
July 1989 - FRANCE - A French farmer shot and killed 14 people including members of his family in the village of Luxiol, near the Swiss border. He was wounded and captured by police.
December 1989 - CANADA - A 25-year-old war movie fan with a grudge against women shot dead 14 young women at the University of Montreal, then killed himself.
November 1990 - NEW ZEALAND - A gun-mad loner killed 11 men, women and children in a 24-hour rampage in the seaside village of Aramoana. He was killed by police.
September 1995 - FRANCE - A 16-year-old youth ran amok with a rifle in the town of Cuers, killing 16 people and then himself after an argument with his parents.
March 13, 1996 - BRITAIN - A gunman burst into a primary school in the Scottish town of Dunblane and shot dead 16 children and their teacher before killing himself.
April 28, 1996 - AUSTRALIA - A gunman unleashed modern Australia's worst mass murder when he shot dead 35 people at the Port Arthur tourist site in the southern state of Tasmania.
April 1999 - USA - Two heavily-armed teenagers went on a rampage at Columbine High School in Littleton, Colorado, killing 13 students and staff before taking their own lives.
July 1999 - USA - A gunman killed nine people at two brokerages in Atlanta, after apparently killing his wife and two children. He committed suicide five hours later.
June 2001 - NEPAL - Eight members of the Nepalese Royal family were killed in a palace massacre by Crown Prince Dipendra who later turned a gun on himself and died few days later. His youngest brother also died later raising the death toll to 10.
April 26, 2002 - GERMANY - In Erfurt, eastern Germany, a 19-year-old gunman opened fire at a school, killing 12 teachers, a secretary, two students and a policeman before killing himself.
October 2002 - USA - Two men killed 10 people in sniper-style shooting deaths that terrorized the Washington, D.C., area.
April 16, 2007 - USA - A gunman killed 32 people and himself at Virginia Tech, a university in Blacksburg, Virginia.
September 23, 2008 - FINLAND - A student opened fire in a vocational school in Kauhajoki in northwest Finland, killing nine other students and one staff member, then killed himself.
March 11, 2009 - GERMANY - A 17-year-old gunman dressed in black combat gear killed nine students and three teachers at a school near Stuttgart. He also killed one other person at a nearby clinic. He was later killed in a shoot-out with police.
November 5, 2009 - USA - A gunman opened fire at Fort Hood, a U.S. Army base in Texas, killing 13 people and wounding 31. An Army major is charged in connection with the rampage.
June 2, 2010 - BRITAIN - A gunman opened fire on people in towns across the rural county of Cumbria. Twelve people were killed and 11 injured. The gunman then killed himself.
July 22, 2011 - NORWAY - A gunman blew up a government building in Oslo and then opened fire at a youth summer camp of Norway's ruling political party, on the holiday island of Utoeya, killing 77 people.
July 20, 2012 - USA - A masked gunman killed 12 people and wounded 58 when he opened fire on moviegoers at a showing of the Batman film "The Dark Knight Rises" in Aurora, a suburb of Denver.
August 5, 2012 - USA - A gunman opened fire during Sunday services at a Sikh temple in Oak Creek, Wisconsin. He killed six people before he was shot dead by police.
December 14, 2012 - USA - A heavily armed gunman killed at least 20 children and six adults at an elementary school in Newtown, Connecticut, and a body was found elsewhere in the town. The gunman was also dead.
(Writing by David Cutler, London Editorial Reference Unit; Editing by Mohammad Zargham)