AURORA, Colo. – As the new Batman movie played on the screen, a gunman dressed in black and wearing a helmet, body armor and a gas mask stepped through a side door. At first he was just a silhouette, taken by some in the audience for a stunt that was part of one of the summer's most highly anticipated films.

But then, authorities said, he threw gas canisters that filled the packed suburban Denver theater with smoke, and, in the confusing haze between Hollywood fantasy and terrifying reality, opened fire as people screamed and dove for cover.

At least 12 people were killed and 58 wounded – 11 critically – in one of the deadliest mass shootings in recent U.S. history.