President Barack Obama travels to Colorado on Sunday to meet families bereaved after a "demonic" gunman went on a shooting rampage at a movie theater in a Denver suburb, killing at least 12 people and wounding 58.
The victims, who ranged from six to 51 years of age, died in Aurora, Colorado, early on Friday when a gunman police identified as graduate-school dropout James Holmes opened fire during a packed midnight premiere of the latest "Batman" film.
A vigil is scheduled for 6:30 p.m. on Sunday in front of Aurora City Hall, organized by civic, community and religious leaders.
"We can now start the natural process of grieving and healing," Aurora Mayor Steve Hogan said at a memorial late on Saturday for one young shooting victim: "We're still reeling."
Obama's trip comes as investigators are deepening a probe into Holmes. He was arrested immediately after the fatal spree at the local multiplex and local and federal authorities disarmed explosives in his booby-trapped apartment on Saturday.
Aurora Police Chief Dan Oates said the shooting followed months of "calculation and deliberation," as Holmes received a "high volume" of deliveries of weaponry to both his work and home.
Colorado Governor John Hickenlooper, speaking on NBC television's "Meet the Press" program on Sunday, said there were still no clues as to the motive for the shooting. But he said Holmes was "a twisted, really delusional individual" who had not been cooperating with authorities.
"He was diabolical, demonic," Hickenlooper said.
"I think of him almost as a terrorist. He wanted to take away, not just from the people here but from the country, our ability to enjoy life," he said.
Sources familiar with the investigation said that some 30 shells filled with gunpowder were found in Holmes' apartment, together with containers filled with "incendiary liquids" intended to fuel a fire from the initial explosions, as well as bullets meant to ricochet around the apartment.
On Saturday afternoon, the local coroner's office released the names of the 12 people killed, including those of a six-year-old girl, a young man celebrating his 27th birthday and an aspiring sportscaster who had barely escaped a shooting in a Toronto mall earlier this summer.
The mass shooting stunned the nation and evoked memories of the 1999 massacre at Columbine High School in Littleton, 17 miles from Aurora, where two students opened fire and killed 12 students and a teacher.
It also reverberated in the U.S. presidential race. Both President Barack Obama and his Republican rival, Mitt Romney, toned down their campaigns on Friday, pulled ads from Colorado and dedicated scheduled events to the victims.
In Rome on Sunday, Pope Benedict expressed dismay and sadness at the shooting.
"I was deeply shocked by the senseless violence which took place in Aurora, Denver," he said in his regular Sunday Angelus address.
"I share the distress of the families and friends of the victims and the injured, especially the children," he said.
Those who witnessed the shooting told of a horrific scene, with dazed victims bleeding from bullet wounds, spitting up blood and crying for help.
Holmes was arrested minutes later in a parking lot behind the cinema. He was armed with an AR-15 assault rifle, a 12-gauge shotgun and a Glock .40-caliber handgun. Police found an additional Glock .40-caliber handgun in his car. All the weapons were legally bought in the previous 60 days.
Holmes was being held in solitary confinement to protect him from other prisoners, a routine move in high-profile cases, said Grayson Robinson, sheriff of Arapahoe County.
Authorities said Holmes had dyed his hair red and called himself "the Joker" in a reference to Batman's comic-book nemesis, was due to make an initial court appearance on Monday.
Little has surfaced from his past to suggest he was capable of such violence.
Until last month, Holmes was studying for a doctoral degree in neuroscience at the University of Colorado's Anschutz Medical School, a few blocks from his apartment.
The University of Colorado Hospital, which treated some of the shooting victims, said 10 people had been released and five remained in critical condition. The Medical Center of Aurora said four of its seven patients remained in intensive care, while three others were on the main trauma floor.
A memorial of flowers, candles and stuffed animals quickly sprung up where the shootings took place. A handwritten sign read: "7/20 gone not forgotten."
At one of the first vigils, about 500 people gathered for a memorial service at Gateway High School on Saturday evening to remember recent graduate A.J. Boik, 18, a talented artist who had been bound for college in the fall.
"He was a very big part of this community," said Tami Avery, 41, whose son played sports with Boik. "He will be dearly missed."