• 2011 Norwegian Anders Behring Breivik drew international attention and anger over a mass killing spree that killed 77 people, mostly teenagers, and cast a pall for weeks after the shooting. He survived the shooting and was sentenced to at least 21 years in prison.
• 2012 Newtown gunman Adam Lanza, whose motives were unknown in the months after the shooting, may have been inspired by Breivik’s own shooting, with some sources noting to CBS News that he may have chosen Sandy Hook because it was the closest target with a large number of people. Lanza may have left evidence showing he was reportedly “obsessed” with Breivik. source

» A caveat: Be careful not to overly lean on this speculation, however. After CBS published their story, they added this note: “In response to this piece, Lt. J. Paul Vance of the Connecticut State Police told CBS News that the investigation into the motive for the Newtown shooting has not been completed and therefore any statements about the shooter’s intent are mere speculation.”