A New York City police officer watches as movie patrons arrive for a screening of "The Dark Knight Rises," Friday, July 20, 2012 in New York. A gunman in a gas mask barged into a crowded Denver-area theater during a midnight premiere of the Batman movie on Friday, hurled a gas canister and then opened fire, killing 12 people and injuring at least 50 others in one of the deadliest mass shootings in recent U.S. history. NYPD commissioner Ray Kelly said the department was providing the extra security at theaters "as a precaution against copycats and to raise the comfort levels among movie patrons." (AP Photo/Mark Lennihan)