Here's what we know about the alleged Colorado shooter.
He is 24 years old and attended high school in San Diego California. He was student at University of Colorado School of Medicine studying Neurology.
According to police, Holmes was armed with an AR-15 rifle, a 12-gauge shotgun and two .40-caliber handguns at the time of the shooting. He was wearing head-to-toe tactical gear as well as a gas mask.
He was dressed a the Batman villain Joker when he entered the theater, according the NYPD.
Local news reports claim that Holmes purchased a ticket to Batman, sat and watched for about 15 minutes. He then left out of the emergency exit and returned to his car. This is when he grabbed his weapons and began the assault.
According to Aurora Police Holmes shot 71 people. 12 are now dead.
His apartment is rigged with trip wires and explosives. Authorities are not sure when they will be able to disarm them all.
He is currently in custody of police.