AURORA, Colo. -- A Colorado shooting suspect's apartment posed a "vexing problem" for officers on Friday as they faced challenges in determining how to safely enter the unit where booby traps were set, a police chief said.
Firefighters were monitoring the Aurora apartment building for gases in an effort to determine what chemicals they say 24-year-old James Holmes might have used inside the place -- in case the materials go off, authorities said.
Holmes is the suspect in a mass shooting Friday at a midnight screening of "The Dark Knight Rises." Twelve people were killed in the attack and dozens were injured, including 11 victims who remained in critical condition, authorities said.
"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.
FBI agents and police who went there discovered it was booby-trapped when they used a camera at the end of a 12-foot pole to look inside.
Aurora Police Chief Dan Oates said photos of Holmes' apartment appeared to also show jars full of ammunition and liquid and other items.
"I personally have never seen anything like what the pictures show us is in there," Oates said.
Officers will try to gain entry on Saturday, he said.
The building and several around it were evacuated, but police on Friday evening escorted residents in ones and two to their apartment units so they could quickly gather personal items.
Roberto Martinez, who lives in a building next door to the suspect's building, hadn't been home since 4:30 a.m. Friday. He was escorted into his apartment and came out with a trash bag filled with items including toiletries, ice, a basketball and some Air Jordans.
He opted to stay in a hotel for the night instead of a shelter at a local high school, where some families with children were staying.
Kaitlyn Fonzi, 20, a graduate student at University Hospital, said she lives in the apartment below that of the suspect.
About midnight, Fonzi said she heard techno-like, deep-based reverberating music coming from that unit apartment. She went upstairs to the suspect's place 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 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 armed SWAT officers 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.