Authorities began disarming trip wires and explosive devices on Saturday inside the apartment of James Holmes, the man suspected of killing 12 people at a screening of "The Dark Knight Rises" at a movie theater near Denver on Thursday night.
Hoping to find clues to Holmes' motive without destroying key evidence in a blast, federal authorities detonated one small explosive and disarmed another inside his suburban Denver apartment. Several other explosive devices remained, said Aurora police Sgt. Cassidee Carlson.
Makeshift memorials sprang up for the 12 victims, 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.
Law enforcement officials on Saturday 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.
Federal officials said 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 with some injuries that could be permanent.
In his Saturday radio address, U.S. 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; Alex Sullivan, who was celebrating his 27th birthday; Jessica Ghawi, an aspiring sportscaster who survived a recent Toronto mall shooting; U.S. Navy sailor John Larimer; and 6-year-old Veronica Moser.
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 theatergoers. 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.
Prime Minister Benjamin Netanyahu sent his condolences to the victims' families on Saturday. In a letter to President Obama, Netanyahu wrote that, on behalf of the people of Israel, he sent "wishes for a full and speedy recovery to the wounded.
"All Israelis stand with the American people as they grieve this horrific tragedy that claimed the lives of so many. We well understand the pain and the loss you are experiencing," he added.
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