AURORA, CO - UPDATE:
At least 12 people were killed and 50 were being treated at Denver area hospitals after a shooting at a midnight showing of Batman, the youngest a 3-month-old baby.

Twelve people were taken to the Medical Center of Aurora with gunshot wounds and ranged from minor to critical condition. Three were treated for chemical exposure, most likely from tear gas. They ranged in age from 16 to 31.

Denver Health had seven victims - one in critical and the rest in fair condition.

The University of Colorado hospital was treating 21 people, including the baby, for gunshot wounds. The oldest is 45. A 6-year-old was being treated at Children's Hospital Colorado, where a total of six victims ranging were taken. The oldest patient there is 31. Their condition wasn't known.

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A gunman opened fire early Friday at a suburban Denver movie theater on the opening night of the latest Batman movie "The Dark Knight Rises," killing 12 people and injuring at least 50 others, authorities said.

The gunman, who is in custody, stood at the front of the theater and fired into the crowd about 12:30 a.m. MDT at a theater at a multiplex theater in a mall in Aurora.

"Witnesses tell us he released some sort of canister. They heard a hissing sound and some gas emerged and the gunman opened fire," Aurora Police Chief Dan Oates said at a news conference.

Police, ambulances and emergency crews swarmed on the scene after frantic calls started flooding the 911 switchboard, officials said.

Officers found the gunman near a car behind the theater.

The suspect was taken into custody, but no name was released. Oates said there's no evidence of any other attackers. There was also no immediate word of any motive.

The suspect spoke of "possible explosives in his residence. We are dealing with that potential threat," Oates said, without providing details on where that was.

He said police also checked for explosives in the parking lot and at the Century 16 theater and secured those areas.

Witness Hayden Miller told KUSA-TV that he was inside Theater 16 and heard several shots.

"Like little explosions going on and shortly after that we heard people screaming," he told the station.

Hayden said at first he thought it was part of a louder movie next door. But then he saw "people hunched over leaving theater."

Aurora is located on the southeast outskirts of Denver, about 10 miles from downtown.