Follow live coverage of Denver shooting at Batman screening
A gunman wearing a gas mask set off an unknown gas before firing into a crowded cinema in Denver, killing at least 12 people and injuring at least 50 others, police said.
The shooter, a man in his 20s, was arrested shortly after the midnight attack near a car outside the multiplex theatre in Aurora, suburban Denver.
US President Barack Obama cut short his election campaign in Florida but addressed an audience in Fort Myers about the shooting before he headed back to Washington.
"There are going to be other days for politics. This, I think, is a day for prayer and reflection," Mr Obama told supporters.
