Police have identified the gunman who opened fire on a crowded Colorado movie theater as 24-year-old medical student James Holmes.
At least 12 people were killed and dozens more were wounded when Holmes opened fire on the audience of a midnight showing of "The Dark Knight Rises" in the Denver suburb of Aurora.
Survivors say Holmes entered the theater through an emergency exit while wearing a gas mask and body armor, tossed some sort of tear gas canisters into the crowd, and then opened fire.
"He walks up the stairs, and all I hear is gunshot after gunshot, and there were just women and children screaming, and it was just terrifying," said Jennifer Seeger.
Holmes was arrested shortly after the attack in the parking lot of the theater.
Police say his nearby apartment was "booby-trapped" with several explosive devices that they're still working to defuse.
"There are some chemical elements there and there are also some incendiary elements. They're linked together with all kinds of wires. As a layman, it's not something I've ever seen before," Aurora Police Chief Dan Oates said.
The FBI says there are no known terrorist links to the massacre.
Sources say Holmes was studying neuroscience at the University of Colorado until last month, when he withdrew from the school.