A gunman at a Connecticut elementary school killed 27 people, including 18 children on Friday. It is among the world's worst mass shootings. Here is a look at some others:
— Aug. 5, 2012: Army veteran Wade Michael Page kills five men and one woman and wounds three other people, including a police officer, before taking his own life at the Sikh Temple of Wisconsin outside Milwaukee.
— July 20, 2012: At least 12 people are killed when a gunman enters an Aurora, Colorado, movie theatre, releases a canister of gas and then opens fire during opening night of the Batman movie "The Dark Knight Rises." James Holmes, a 24-year-old former graduate student at the University of Colorado, has been charged in the deaths.
— March 11, 2012: Sixteen Afghan villagers, including nine children, are killed during a predawn attack in which Army prosecutors have charged Staff Sgt. Robert Bales, 39.
— July 22, 2011: Confessed mass killer Anders Behring Breivik kills 77 in Norway in twin attacks: a bombing in downtown Oslo and a shooting massacre at a youth camp outside the capital. The self-styled anti-Muslim militant admitted both attacks.