Shooter Kills 14 In Movie Theater

Tom Sullivan, center, stands with family members outside Gateway High School where witness were brought for questioning after a gunman opened fire at the midnight premiere of The Dark Knight Rises Batman movie today in Aurora, Colo. Sullivan later pleaded with the media to help find his missing son, Alex Sullivan, who attended the movie to celebrate his 27th birthday. A gunman wearing a gas mask set off an unknown gas and fired into the crowded movie theater killing 12 people and injuring at least 50 others, authorities said. (AP Photo/Barry Gutierrez)

A gunman wearing a gas mask set off an unknown gas and fired into a crowded movie theater in suburban Denver theater at a midnight opening of the Batman movie “The Dark Knight Rises,” killing 14 people and injuring at least 50 others, authorities said. Moviegoers didn’t know what was happening and some thought the attack was part of the show. Then they saw a silhouette of a person in the smoke at the front of the theater near the screen, pointing a gun at the crowd. “I told my friend ‘we’ve got to get out of here,’ but then he shot people trying to go out the exits,” Jennifer Seeger told NBC’s “Today.” She the shooter made his way up the aisle, shooting as he went, saying nothing. Some of those injured are children, and victims are being treated for chemical exposure apparently related to canisters thrown by the gunman. The shooter, a man in his 20s, was arrested shortly after the attack at 12:30 a.m. MDT at the multiplex theater at a mall in Aurora/ AP . More here.

Question: Why do these massacres happen at intervals in American society?