An investigator kneels next to a gas mask marked as evidence outside the Century 16 movie theater east of the Aurora Mall in Aurora, Colo. on Friday, July 20, 2012. A gunman in a gas mask barged into the crowded Denver-area theater during a midnight showing of the Batman movie on Friday, hurled a gas canister and then opened fire in one of the deadliest mass shootings in recent U.S. history. (AP Photo/David Zalubowski)