As they filed into the cinema, film-goers took to Twitter to share their excitement. “It's going to be a good night!” wrote one young woman, as she waited for the curtain to rise on a midnight screening of the new Batman film The Dark Knight Rises.
But roughly 25 minutes later, things took a sinister turn. "Things are nuts right now," wrote Isaac Ramos. Domnick Bivins tweeted: "I literally just seen a little girl get carried out with bullet wounds."
In the early hours of yesterday morning, a gunman burst into auditorium nine of the Century 16 multiplex in Aurora, a suburb of Denver, where customers were attending at a special late-night screening of the film. He was wearing a gas mask, bullet-proof vest and black combat clothing. After kicking open a fire escape, and tossing two tear-gas grenades into the crowd, he walked into the auditorium and opened fire. At least a dozen people were killed and 38 injured.
It was America's worst mass shooting since the Virginia Tech tragedy in 2007, and took place just half an hour's drive from Columbine High School, where 12 students and a teacher were murdered by two students in 1999.
Police said the man suspected of the shooting – 24-year-old James Holmes – may have based his outfit on that of the Batman movie's villain, Bane, a terrorist who carries out a series of indiscriminate and at times graphic public attacks in Gotham City. A different report suggested Holmes had dyed his hair red and that when he walked in he said: "I am the Joker" – referring to another Batman villain.
Barack Obama and his Republican challenger, Mitt Romney, responded by temporarily suspending their presidential campaigns. The President, who was in Florida, said he was "shocked and saddened" by the "horrific" attack and returned to the White House.
Survivors said they initially thought the cinema invasion was all part of the show, which many fans attended in fancy dress. They said the suspect – who carried what the FBI called an "AK-type" assault rifle along. a shotgun and two Glock handguns – strode into the auditorium and, without speaking, fired several shots into the air before targeting the audience.
"It was scary. He waited for both the [tear-gas] bombs to explode before he did anything. Then he began to shoot. He had no specific target. He just started letting loose," an witness told the local 9News TV network.
A survivor, Jennifer Seeger, was feet away from the gunman. "Every few seconds it was 'boom, boom, boom'," she said. "He would reload and shoot and anyone who would try to leave would get killed."
Video footage of the aftermath of the attack shows crowds fleeing into the car park. "It was chaotic," another witness said. "We heard screaming from other theatres. I walked out and there was a girl shot in her knee – holding on to her mom and crying." Some casualties appear to have been caused by bullets which pierced the walls and went into an adjacent auditorium.
Mr Holmes was arrested outside the building at about 1am. He was holding a rifle and handgun when police found him, but a spokesman told reporters: "He did not put up a fight."
The suspect is due to make his first court appearance on Monday.
Gun laws: No Change since Columbine
The 1999 massacre at Columbine High School, just 30 miles away, led to a campaign to tighten gun control in Colorado. But the state still has some of the most lenient gun laws in the US. Any resident over 18 with no criminal record can buy a firearm - no permit or registration is needed. Guns can even be taken on to university campuses, and can be carried in full view.