A gunman at a Connecticut elementary school killed more than two dozen people, including 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: Twelve people are killed when a gunman enters an Aurora, Colo., movie theater, 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.