Holmes reportedly threw one canister towards the left side of the theatre, emitting a gas or smoke, that partially obscured the audience members' vision, made their throats and skin itch, and caused eye irritation. He fired a 12-gauge Remington 870 Express Tactical shotgun, first at the ceiling and then at the audience. He also fired a Smith & Wesson M&P15 semi-automatic rifle with a 100-round drum magazine, which eventually malfunctioned. Finally, he fired a .40-caliber Glock 22 Gen4 handgun. He shot first to the back of the room, and then toward people in the aisles. A bullet passed through the wall and hit three people in adjacent theater 8, which was screening the same film. Witnesses said the multiplex's fire alarm system began sounding soon after the attack began, and staff told people in Theater 8 to evacuate.
