Bomb techs say 30 softball-sized improvised explosive devices have been found in the Aurora, Colorado apartment of James Holmes, the man suspected of killing 12 people and wounding 58 others at a movie screening late Thursday night.

Aurora’s police chief indicated that the explosives inside the shooting suspect’s apartment are mostly under control. “We believe we’ve eliminated most of the threat there,” he said.

The FBI has confirmed that the most dangerous wire trap was connected to the door of the apartment, and anyone who had opened the door would have been seriously injured or killed.

Earlier, a controlled detonation was successfully performed inside the suspect’s apartmen, Aurora PD said. They next plan to remove other items from the apartment that could explode, including about 30 shells that will be placed in sand trucks and taken to a disposal site.

Five nearby buildings have been evacuated, and law enforcement officials are discussing ways of detonating or disarming the explosives, according to media reports on the ground.

Aurora police chief Daniel Oates said the apartment was booby-trapped with various incendiary devices and chemical devices connected to trip wires. He added that the explosives are so complex, “police could be on the scene for hours or days.”

The police used robots to examine the suspect’s residence without putting officers’ lives in danger. Now they plan to detonate the devices remotely rather than try to defuse them.

Kaitlyn Fonzi, who lives in the apartment below, said that she heard loud techno-like, deep-bass reverberating music coming from Holmes’ flat around the time of the massacre. She went to check on it, but decided not to confront the owner of the flat despite the fact that the door was open.

“I’m concerned if I had opened the door, I would have set it off,” she said.

She said she believes the music was on a timer because it started about the time of the shootings.

According to the tenants, the building is quiet and populated largely by students and doctors affiliated with a nearby University of Colorado Denver medical campus.

Ben Leung, a 27-year-old pharmacy student, told local media he lives on the first floor of the same building as the suspect, James Holmes. In a phone interview Leung said only people affiliated with the University of Colorado at Denver are allowed to live in the building.

Leung said he went to bed shortly after midnight, then awoke when police in riot gear banged on his door and told him the building was being evacuated. “At that time I had no idea what was going on,” he said.

Meanwhile, the Pentagon spokesman has told reporters that US service members appear to be among the casualties of the shooting.

According to the Department of Defense, 2 Air Force reservists and 2 Navy service member were among the injured, and are being treated in a hospital.

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A fire truck ladder is pictured outside the Denver shooting suspect’s apartment building in Aurora Colorado, July 20, 2012 (Reuters / Jason Hatfield)

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Aurora Police officers are pictured outside an apartment building in Aurora Colorado, July 20, 2012 (Reuters / Jason Hatfield)

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FBI officers, Aurora police officers, and fire crews are pictured outside the Denver shooting suspect’s apartment building in Aurora Colorado, July 20, 2012 (Reuters / Jason Hatfield)

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FBI officers, Aurora police officers, and fire crews are pictured outside the Denver shooting suspect’s apartment building in Aurora Colorado, July 20, 2012 (Reuters / Jason Hatfield)