The suspect in a U.S. movie theater massacre has been charged with multiple counts of first degree murder and attempted murder in the shooting attack, in which 12 people were killed and 58 wounded.

Prosecutors formally filed charges against suspect James Holmes in Colorado on Monday. They say they may seek the death penalty in the case.

Authorities say Holmes went on a shooting rampage in the Colorado city of Aurora. The July 20 attack took place during the midnight screening of the new Batman film The Dark Knight Rises. Police say Holmes threw a tear gas bomb in the theater before opening fire on the audience.

During his first court appearance a week ago, the suspect appeared dazed and unemotional.

Holmes – a former Ph.D. student in neuroscience – has refused to talk to police.