At least 12 people were killed and 50 wounded after an armed gunman opened fire during an early morning screening of the new Batman movie, The Dark Knight Rises at an Aurora, Colorado movie theatre.

One of the victims was just 3 months old, according to hospital workers.

Police arrested a man in his early 20s in the rear parking lot of the theatre who is to believed to be the shooter.

“He did not resist.  He did not put up a fight,” said Frank Fania, a police spokesman.

The shooting broke out during the viewing of the movie at the Century Aurora 16 theatre when the gunman kicked in an emergency exit door and threw a smoke bomb into the audience before opening fire, according to witnesses.

“We just heard a pop, pop, pop, pop,” said Quentin Caldwell, who was watching the Batman movie in another theatre.

Initially it was reported that 14 had died, but it has now been updated to 12 dead and several people remain in critical condition at area hospitals.

Aurora is a suburb of Colorado, which is about 13 miles from the site of the Columbine High School shooting in April 1999, where two high school students killed 13 and wounded 23.