James Holmes’s semiautomatic assault rifle jammed during the attack that killed 12 people and left 58 wounded at an Aurora, Colorado, screening of The Dark Knight Rises, a source told the Associated Press on Sunday. The source, a federal law enforcement official, said a weapon with a 100-round drum magazine—which can fire 50 to 60 rounds per minute—was recovered at the scene; Holmes reportedly had to switch to a weapon with less firepower after the first one jammed. Holmes, 24, opened fire at a midnight showing of the new Batman movie on Friday. A law enforcment official told the Associated Press that a Batman mask had been found inside Holmes's apartment. Aurora police chief Dan Oates also said that Holmes had "lawyered up" and would not cooperate with police.