FOURTEEN people died today when a gunman opened fire during a US screening of the latest Batman movie.
Police said at least 50 others were injured during the shooting at the Aurora Mall in Colorado.
The violence erupted as The Dark Knight Rise was playing at the Century 16 cinema.
Aurora police chief Dan Oates said: “Witnesses tell us he released some sort of canister.
“They heard a hissing sound and some gas emerged and the gunman opened fire.”
Police, ambulances and emergency crews rushed to the scene after frantic calls started flooding in to the 911 switchboard.
Officers found the gunman near a car behind the building.
“A gas mask, rifle, handgun at least one additional weapon (were) found inside” he said.
The suspect was taken into custody, but no name was released.
Mr Oates said there was no evidence of any other attackers. There was also no immediate word of any motive.
It was claimed that the suspect spoke of possible explosives at his home and Mr Oates said the police were dealing with the potential threat.
Mr Oates added officers also checked for explosives in the car park and cinema, securing those areas.
Witness Hayden Miller said he was inside the building when he heard several shots.
Mr Miller said it sounded “like little explosions”.
“Shortly after that we heard people screaming,” he added.
Mr Hayden said he initially though the noise was part of a louder film next door until he saw people hunched over leaving the cinema.
Radio reporter Brenda Stuart said other movie-goers also thought the attack was part of the film at first.
She said: “A lot of people thought the gunshots were part of the movie.
“Then bullets started flying.”
The police chief said 10 victims died at the cinema and four at area hospitals.
Two people in critical condition were rushed to the nearby Swedish Medical Centre, spokeswoman Nicole Williams said.
She said emergency crews told staff to prepare for several more patients from the shooting scene.
“We’re on standby to receive,” she said.
Aurora is on the south-east outskirts of Denver, about 10 miles from the city centre.
The youngest reported victim was a three-month old. Six children were being treated at Children’s Hospital Colorado, but their conditions were not known.