At least 14 people were killed and about 50 injured as a gas mask-wearing gunman opened fire early Friday at a suburban Denver movie theatre during a premiere showing of the new Batman movie.

A 24-year-old suspect is in custody and an apartment building in north Aurora, about 10 miles (16 km) from downtown Denver, connected to the suspect was being evacuated and searched for possible explosives, DenverPost.com reported citing police chief Dan Oates.

Ten people died at the scene and four others died at hospitals in the shooting at the Aurora Mall, where three theatres were showing the latest Batman movie "The Dark Knight Rises". Most of the wounded and killed were at Theatre 9.

Oates said there was no evidence of a second suspect, but the man in custody had made a statement about possible explosives in his residence. There was also no immediate word of any motive.

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

The violent and chaotic scene erupted about 12.30 a.m. local time as a gunman stood at the front of one of the Century 16 theatres at the Aurora Mall, CBS reported.

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

Officers found the gunman near a car behind the theatre. "A gas mask, rifle, handgun at least one additional weapon (were) found inside," they said. A CBS correspondent reported one of the weapons was an AK-47 assault rifle.

President Barack Obama, who was notified about the shooting by homeland security adviser John Brennan, said he is "shocked and saddened" by the "horrific and tragic" shooting.

The FBI said that there is no indication that the shooting has any connection to terrorism.

An amateur video posted to Youtube showed people walking around outside the theatre, allegedly in the moments after the incident.

One man was seen wearing a shirt that appeared to be bloodstained. He was being led by a police officer. Some people could be heard shouting.

A witness, Hayden Miller, told KUSA-TV that he was inside Theatre 16 and heard several shots.

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