A gunman in a gas mask and bullet-proof vest killed 12 people at a midnight premiere of the new Batman movie "Dark Knight Rises" in a suburb of Denver.

The gunman, 24-year-old James Holmes, hurled a gas canister into an auditorium and opened fire on moviegoers as they were trying to leave.

When Holmes was apprehended by police, he mentioned explosives in his nearby apartment, according to several reports.

"The suspect booby-trapped his Aurora apartment with sophisticated explosives," said Aurora Police Chief Dan Oates at a news conference, according to Reuters.

"We are trying to determine how to disarm the flammable or explosive material. We could be here for hours or days," Oates added. "The pictures are fairly disturbing. It looks very sophisticated, how it's booby-trapped. It could be a very long wait."

Police lifted his third-floor window by a crane and searched the suspect's apartment building with a remote camera.

Firefighters, police and sheriff's deputies from several jurisdictions swarmed the scene with heavy weaponry and trucks from the bomb squad, according to the report.

Residents at Holmes' apartment building in north Aurora were evacuated around 2 a.m. while police searched the third floor of the building, according to The News Herald.

Resident Wes Bradshaw and his mother revealed to the newspaper that they watched the search from their apartment. The two watched a police robot enter the building right before they heard a small explosion, according to the report.

The two and the rest of the building's residents were ordered to evacuate shortly after the explosion.

As residents of the area waited outside for updates, local police at the scene told them it could be hours before they are allowed to return to their homes.

Emergency crews were seen entering the suspect's third-floor apartment. Using a long pole, responders broke into the window from the basket atop of a hook and ladder truck, the report also stated.

FBI was on scene as well as local fire, police and Adams County Sheriff's deputies. Workers are approaching the window three at a time. They were also seen wearing helmets and flak vests while they looked into the apartment.

Six local hospitals reported receiving 55 patients from the scene. Ten victims died in the theater and two died in the hospital, according to Reuters.

We reported earlier that White House officials saw no connection to terrorism, according to a spokesman for Obama.

Tags: James Holmes Dark Knight Rises colorado shooting