In the wake of one of the worst shootings in U.S. history, movie theaters across the nation are ramping up security to protect patrons and employees from copycat incidents. Shortly after midnight Friday during a showing of “The Dark Knight Rises,” a gunman wearing a gas mask and black SWAT gear set off a gas canister and then opened fire inside a crowded theater in the Denver suburb of Aurora, Colo., killing 12 people and wounding 59 others, authorities said. The suspect, 24-year-old James Holmes, was arrested near a car behind the theater.