2012 : Newtown , Connecticut , police came to school grounds with four weapons . Guns included a shotgun , an AR-15 rifle , a Barrett 10 mm and a Sig Sauer 9 mm . Unlike the military version , the AR-15 is a semiautomatic , firing one bullet per squeeze of the trigger . Lanza used numerous empty magazines to load his rifle , police say . The shotgun was found in Lanza 's parked car , police say .
2012 : Newtown , Connecticut , police came to school grounds with four weapons . Guns included a shotgun , an AR-15 rifle , a Barrett 10 mm and a Sig Sauer 9 mm . Lanza used numerous empty magazines to load his rifle , police say . The shotgun was found in Lanza 's parked car , police say .