AURORA, Colo. — Colorado firefighters Friday began monitoring an apartment building for gases in an effort to determine what chemicals one of its residents might have used to booby trap the place.
The resident, James Holmes, 24, is the suspect in a mass shooting early Friday at a movie theater about 4 miles away.
"It's a pretty extensive booby trap. We're not sure what it's attached to. There are trip wires. There are three containers, and we don't know what's inside," said Chris Henderson, deputy Aurora fire chief.
If there is a detonation that causes a fire, firefighters will fight it from the outside of the building, he said.
The building and several around it were evacuated.
Kaitlyn Fonzi, 20, a graduate student at University Hospital, said she lives in the apartment below Holmes' residence.
About midnight, Fonzi said she heard techno-like, deep-bassed reverberating music coming from the unit above. She went upstairs to the apartment and put her hand on the door handle. She felt it was unlocked, but she didn't know if he was there and decided not to confront him.
"I yelled out and told him I was going to call the cops and went back to my apartment," she said.
Fonzi called police, who told her they were busy with a shooting and did not have time to respond to a noise disturbance. She said she was surprised to learn later that the apartment was booby trapped and was shaken by the news.
"I'm concerned if I had opened the door, I would have set it off," she said.
Fonzi said she had seen the man one or two times before but never talked with him.
She said she believes the music was on a timer because it started about the time of the shootings.
Police have searched apartments and broken out windows at the building, but Fonzi said she doesn't know the condition of her apartment or car.
When asked about plans to possibly try to detonate the device with a robot, she said, "It's not an ideal situation, but if that has to be done to keep safe, then it has to be done."
University of Colorado pharmacy student Ben Lung, 27, who lives two floors down from the suspect, said he and other residents were evacuated around 2 a.m. by SWAT officers armed with rifles.
"I heard a loud crash. It sounded like an air conditioner falling to the ground. About 10 minutes later, I heard police knock on my door. Police were armed with assault rifles, and they brought us outside the apartment building and started questioning us," Lung said.
Lung said a few residents upstairs had called police around midnight and complained about loud music coming from the suspect's apartment.
Michelle Thuis, 26, who lives in an apartment near the entrance to the building, said police woke her up when they stormed in around 2:30 a.m.
"I heard them breaking down the front door. I called the police on them, then I looked out and saw it was the police," she said.
Thuis described the building as quiet and populated largely by students and doctors affiliated with a nearby University of Colorado Denver medical campus.
The American Red Cross set up a shelter at Aurora Central High School for people evacuated from their residences because of the police search and monitoring.