AURORA, Colo. (AP) -- Authorities on Saturday began disarming trip wires and explosive devices "set up to kill" inside the apartment of the suspect in the deadly Colorado movie theater shooting, hoping to find clues to his motive without destroying key evidence in a blast.
Federal authorities detonated one small explosive and disarmed another inside James Holmes' suburban Denver apartment, but several other explosive devices remained, said Aurora police Sgt. Cassidee Carlson.
Makeshift memorials sprang up for the 12 victims, including a U.S. navy sailor, an aspiring sportscaster and a man celebrating his 27th birthday, after police grimly went door to door with a list of those killed in the worst mass shooting in recent U.S. history. Holmes, 24, was arrested early Friday outside the Aurora theater after witnesses say he unleashed gunfire and gas canisters on a crowd of moviegoers watching the midnight showing of the new Batman film, "The Dark Knight Rises."
On Saturday, law enforcement officials began trying to disarm up to 30 devices in Holmes' booby-trapped apartment, and set off a small explosion to detonate one device.
The devices were "set up to kill that person and that could have been a police officer executing a search warrant," Carlson said. Police planned an intricate procedure to disarm the possible weapons without destroying evidence that could be in the apartment.
"We don't want to lose evidential value," Carlson said.
Federal officials said in a bulletin obtained by The Associated Press that they still hadn't determined a motive for the suspect as families grieved and others waited at hospitals, where seven of the wounded remained in critical condition on Saturday with some injuries that could be permanent.
In his Saturday radio address, President Barack Obama urged Americans to pray "for the victims of this terrible tragedy, for the people who knew them and loved them, for those who are still struggling to recover
The victims included 23-year-old Micayla Medek, said Anita Busch, the cousin of Medek's father. The family took the news hard, but knowing her fate after waiting without word brought them some peace, Busch said.
"I hope this evil act, that this evil man doesn't shake people's faith in God," she said.
Besides Medek, relatives confirmed that Alex Sullivan and Jessica Ghawi were among those killed, Sullivan on his 27th birthday.
Aurora Police Chief Dan Oates said Holmes used a military-style semi-automatic rifle, a shotgun and a pistol to open fire on the unsuspecting theater-goers. He had bought the weapons at local gun stores within the last two months. He also recently purchased 6,000 rounds of ammunition over the Internet, the chief said.
The suspect's stellar academic record, apparent shy demeanor and lack of a criminal background made the attack even more difficult to fathom.
It also wasn't known why the suspect chose a movie theater to stage the assault, or whether he intended some twisted, symbolic link to the film's violent scenes.
The Batman movie, the last in the trilogy starring Christian Bale, opened worldwide Friday with midnight showings in the U.S. The plot has the villain Bane facing Bale's Caped Crusader with a nuclear weapon that could destroy all of fictional Gotham.
The Dark Knight Rises" earned $30.6 million in Friday morning midnight screenings, and, according to industry estimates, roughly $75-77 million on the day. That put it on track for a weekend total of around $165 million, which would be the second highest opening weekend ever, following "The Avengers."
Warner Bros. has announced it would forgo the usual revenue reports until Monday out of respect for the victims. Sony, Disney and Universal also said they would delay reporting box office receipts until Monday, a day later than the routine Sunday releases for Hollywood.
In New York City, Police Commissioner Raymond Kelly said: "It clearly looks like a deranged individual. He has his hair painted red. He said he was the Joker, obviously the enemy of Batman."
Oates would not confirm that information, but did say he spoke to Kelly. Asked whether Holmes had makeup to look like the Joker, Oates said: "That to my knowledge is not true."
Near the entrance to the theater's parking lot, a makeshift memorial of 12 candles sat in a row alongside piles of flowers. Up the hill from the theater, about 20 pastors led a vigil for 350 people, some hugging and crying. A sign read, "7/20. Gone Not Forgotten."
An emotional Gov. John Hickenlooper said earlier Friday that people would not be defined by the tragedy.
"We are clear that we are going to rise back and lift ourselves above this," he said.
A federal law enforcement official said Holmes bought a ticket to the movie, went into the theater as part of the crowd and propped open an exit door as the movie was playing. The suspect then donned protective ballistic gear and opened fire, the official said, speaking on condition of anonymity because he was not authorized to discuss the investigation.
Authorities said Holmes shot scores of people, picking off victims who tried to flee. At least one person was struck in an adjacent theater by gunfire that went through the wall. Adding to the terror and chaos were two gas canisters thrown by the suspect that filled the theater with smoke.
Tanner Coon, a 17-year-old Aurora resident who was watching the film with two friends, said he first thought the gunshots were firecrackers. When he realized what was happening, he ducked between seats and waited for the shooter to bark demands.
"When is he going to start telling us what to do? When is this going to become a hostage situation?" Coon said.
When the firing ended, Coon said he started running up the row but slipped in blood and fell on a woman who was lying on the ground. He tried shaking her, he said, but she didn't respond, so he left her behind and ran from the theater.
The shooting was the worst in the U.S. since the Nov. 5, 2009, attack at Fort Hood, Texas. An Army psychiatrist was charged with killing 13 soldiers and civilians and wounding more than two dozen others. It was the deadliest in Colorado since the 1999 attack at Columbine High School, where two students killed 12 classmates and a teacher and wounded 26 others before killing themselves.
Holmes had enrolled last year in a neuroscience Ph.D. program at the University of Colorado-Denver, though he left last month for unknown reasons. In academic achievement, "he was at the top of the top," recalled Timothy P. White, chancellor at the University of California, Riverside, where Holmes earned his undergraduate degree before attending the Denver school.
Those who knew Holmes described him as a shy, intelligent person raised in California by parents who were active in their well-to-do suburban San Diego neighborhood. Holmes played soccer at Westview High School and ran cross-country before going to college.
Police released a statement from his family Friday that said, "Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved."