"Police said the alleged gunman had three weapons: a Remington shotgun, a Smith & Wesson M&P assault rifle and a Glock .40-caliber handgun. The assault rifle, which is akin to an AR-15 and is a civilian version of the military’s M-16, could fire 50 to 60 rounds per minute and is designed to hold large ammunition magazines. The source said that Holmes allegedly had obtained a 100-round drum magazine that attached to the weapon but that such large magazines are notorious for jamming. The law enforcement official said authorities think the gunman first used the shotgun — some victims have buckshot wounds — and then began using the assault rifle, which jammed. Then he resorted to the handgun."