Witnesses said the gunman wearing a gas mask opened fire and induce one of those smoke or tear gas bomb on the Century Theater in Aurora Mall outside Denver, reported Xinhua citing KUSA-TV.
Radio KOA said 30 to 40 people were injured and a few can have been killed within the shooting.
As many as 20 people were being treated for gunshot wounds, three of them in serious condition, said CNN.
Police said the suspected gunman was in custody.
According to imdb, eight years on, a brand new terrorist leader, Bane, overwhelms Gotham's finest, and the Dark Knight resurfaces to give protection to a city that has branded him an enemy.
The movie have been directed by Christopher Nolan and it stars Christian Bale, Michael Caine and Gary Oldman.
Bejamin Fernandez, a witness, said he was watching the film when he heard a string of blasts. He said that folks ran and there have been gunshots as police shouted "Get down!"
He saw people falling, reported denverpost.com.
Salina Jordan, a 19-year-old, saw people hit.
She said one girl was struck on her cheek and others within the stomach.
It seemed like firecrackers until someone bumped into Theater 8 yelling "they're shooting out here!", said Jordan.
The police rushed in, telling people to run out, she added.
