The suspect in the deadly shootings in Colorado had an assault rifle, a shotgun and two pistols.
A federal law enforcement official says the suspect, identified by other federal law enforcement officials as James Holmes, also used a gas canister in the attack in a movie theater in the Denver suburb of Aurora, Colo. The official spoke on the condition of anonymity to discuss the ongoing investigation.
Officials believe Holmes, who was wearing a gas mask during the attack, killed a dozen people when he open fired in the crowded theater.
Investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives, along with other local, state and federal law enforcement officials, are investigating the overnight attack.
Police say Holmes' apartment is booby trapped, so they've evacuated five surrounding buildings.
Aurora Police Chief Dan Oates says bomb technicians are determining how to disarm flammable or explosive material in the third-floor apartment. He says police could be there some time.
Oates says pictures from inside the apartment are fairly disturbing and the devices look to be sophisticated.
FBI agents and police used a hook and ladder fire truck and put a camera at the end of 12-foot pole inside the apartment where 24-year-old James Holmes lives.
The apartment is about four miles from the theater where at least 12 people were killed and 50 were wounded.