James Holmes, Colorado 'Dark Knight Rises' Shooter, Reportedly Called Himself The Joker (Photo)

The 24-year-old male reportedly booby-trapped his apartment with "sophisticated" explosives.

The shooter behind the movie theater massacre at a midnight screening of The Dark Knight Rises is believed to be James Holmes, a 24-year-old California man who moved to Colorado last year to attend medical school.

Holmes, who has been taken into custody by police, was wearing a gas mask and bulletproof vest as he entered the theater from an emergency exit at the front of the theater, threw a smoke bomb in front of the screen and then opened fire on the audience. NYPD Commissioner Ray Kelly said that he had "his hair painted red, he said he was ‘The Joker,’ obviously the ‘enemy’ of Batman."

The Joker was Batman's enemy in 2008's The Dark Knight, portrayed by Heath Ledger in an Oscar-winning performance. Traditionally, The Joker's hair is green.

At least 12 are dead, with more in critical condition; 57 overall are said to be injured. Police said that Holmes  was carrying an AR-15 assault rifle, Remmington 12-guage shotgun, 40-caliber glock handgun; he also had a 40-caliber glock in the car. It has been confirmed that they were all obtained legally.

STORY: Colorado 'Dark Knight Rises' Shooting Witnesses Describe the Attack

Police that entered his apartment described it as "booby trapped" with sophisticated explosives, and expect to be there for days as they work through the bombs. He had a poster of Will Ferrell in Anchorman on his wall and left the same song playing on repeat. Holmes, a white male, lived in the apartment since May 2011; he was enrolled at the University of Colorado's graduate school, pursuing his PhD in neuroscience, but the AP reports that he withdrew last month.

While Holmes lives on the third floor of his building, all five of the buildings in his complex were evacuated. They are strictly university housing.

A former neighbor described Holmes as "a very nice" guy who was always smiling, according to Rancho Bernardo Patch. The neighbor speculated that he was having trouble finding a job.

His family, who live in San Diego, put out a statement through a spokesperson.

"Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved," they said. "We ask that the media respect our privacy during this difficult time Our family is cooperating with authorities in both San Diego, California, and Aurora, Colorado. We are still trying to process this information and we appreciate that people will respect our privacy."