Denver – An unnamed man who has given an account of what happened at a movie theatre where a gunman has killed 12 people and wounded up to 50 after the shooting has called the incident "madness".
The man, who appears on a video on BBC, said a witness who had been in theatre 9 where the shooting took place had told him of what she had seen.
"What she described, at first...I didn’t translate it quite well. It sounded like madness to me."
The man said the woman, who was unhurt in the incident, told him that a man “about six foot [about 1.8m]” wearing a riot helmet, bullet proof vest, goggles and dressed all in black kicked through the movie theatre’s door.
Upon seeing that he was armed the woman and her boyfriend dropped to the floor and began crawling out of the theatre.
"When she turned around all she saw was this guy slowly making his way up the stairs and just firing at people. Picking random people."
Denver's KOA radio station said a figure in a gas mask had opened fire at the showing in a mall in the suburb of Aurora and set off a smoke or tear gas bomb before shooting erupted.
"This is a horrific event," Aurora Police Chief Dan Oates told a news conference, adding that a suspect was in custody and that there was no evidence of a second gunman.
Dozens of police were at the scene, and the authorities evacuated the area while they checked if there was an explosive device in the area.
Police arrested a male suspect in the parking lot behind the theatre, police spokesperson Frank Fania said. "He did not resist, he did not put up a fight," he said. The suspect's apartment building has been evacuated.
The suspect was thought to be in his early 20s, Fania said. He was carrying a knife, a rifle, a handgun when arrested and one other gun was recovered from the theatre, he said. He also confirmed witness accounts that the gunman was also wearing a bulletproof vest.
The gunman "appeared at the front of the screen" in the theatre and started shooting, Fania said.
Another witness told CNN: "We heard anywhere from 10 to 20 shots and little explosions going on. Shortly after that we heard people screaming. Then they came on PA system and said everyone needed to get out.
"As soon as we got out, there were people running around and screaming." He said friends had told him the gunman was wearing a gas mask.
A third witness said the gunman opened fire during a shoot-out scene in the movie, leading to confusion. The theatre also filled with thick smoke, he said.
Fania said police received the first call about the shooting at 00:39 local time and responded within "a minute or two".
Local hospitals were alerted to a "mass casualty incident". Media reports said 10 people died at the scene and four died later in hospital.
A spokesperson for Denver's Swedish Medical Centre said three people had been admitted to that hospital with gunshot wounds and were in critical condition.
Another hospital, Denver Health, had received six wounded, one of whom was in critical condition, spokesperson Kalena Wilkinson said.