Correction: An earlier version of this article incorrectly described one of the victims, Navy Petty Officer 3rd Class John T. Larimer, as a military officer. Petty officers are enlisted Navy personnel; they are not commissioned officers. This version has been corrected.

The situation was literally explosive in this grieving Denver suburb Saturday as bomb experts disarmed the booby-trapped apartment of James Holmes, who police said spent months amassing explosives, weapons and ammunition and then walked into a movie theater early Friday and began shooting.

The failed neuroscience student, who is scheduled to appear in court Monday, remains an enigma — a young man who, despite troubles in academia so severe that he was quitting his graduate school program, showed no obvious sign of being on the brink of extreme violence.

The police chief, Dan Oates, said he and his officers felt targeted by the elaborate network of explosives in Holmes’s apartment.

“This apartment was designed, I say, based on everything I’ve seen, to kill whoever entered it,” Oates said at a news briefing. “It was gonna be a police officer, okay? Make no mistake about what was going on there. You think we’re angry, we sure as hell are angry.”

Aurora police said Saturday night that all explosives had been removed from the apartment and that FBI agents had gone inside to examine other evidence.

The protracted bomb-squad work at Holmes’s apartment took place on a day when Aurora residents learned the names of the 12 people killed and 58 wounded in the assault at the Century 16 movie theater, where a crowd of mostly young people showed up for the midnight screening early Friday of the new Batman film, “The Dark Knight Rises.”

Among the dead were two members of the military, a man celebrating his 27th birthday and a 6-year-old girl, Veronica Moser-Sullivan, whose 25-year-old mother, Ashley Moser, is in critical condition and semiconscious with multiple gunshot wounds to her throat and abdomen.

President Obama will travel Sunday to Colorado to visit with shooting victims and their families in Aurora, the White House said Saturday night.

Holmes, 24, had no criminal record. He is being held without bond in the Arapahoe County Jail on suspicion of first-degree murder, reportedly in solitary confinement, and although he has not been formally charged, police said there are no other suspects. He is being represented by the public defender’s office.

Police learned from Holmes when they arrested him that his apartment was booby-trapped. It is unclear why Holmes, minutes after allegedly shooting strangers in a movie house, told police about the explosives.

Oates said that for four months, Holmes had been receiving a large number of commercial packages, which the chief said enabled him to assemble the material in the booby-trapped apartment and the small arsenal of weapons and ammunition allegedly used in the massacre.

“What we’re seeing here is evidence, I think, of some calculation and deliberation,” the police chief said.

Detectives had been unable to investigate Holmes’s 800-square-foot third-floor apartment because of the elaborate web of incendiary and chemical devices, numbering about 60 in all. The effort to defuse and disarm the explosives was made all the more delicate by the need to preserve any criminal evidence.

In a hallway just inside the front door, a wire-filament tripwire was strung at waist height, according to a law enforcement source. The tripwire was connected to two containers of chemicals that, when mixed, could create an explosion.

The bomb squad disarmed the setup by sending in a robot that slipped beneath the tripwire and removed one of the bottles of liquid.

Then came 30 spherical canisters in the living room. These resembled fireworks shells packed with gunpowder — “improvised grenades,” the official called them. Wires ran from these devices to a “control box” in the apartment kitchen. It was not clear, the official said, how they were supposed to be detonated.

Authorities used a “bottle shot” — a small explosive charge that sends out a wave of water at high speed — to destroy the control box.

Finally, the official said, there were about three jugs in the living room filled with what appeared to be a combination of liquid and gunpowder. “Improvised napalm,” the official called it. These were not rigged to blow up, but likely would have been set off in a “sympathetic detonation” if the other explosives had been tripped. That would have given the blast extra heat and destructive power.

With the explosives cleared, residents of four adjacent buildings can begin returning home. Some had been staying in emergency shelters and others with friends and relatives.

“It went very, very well,” FBI Special Agent James Yacone said Saturday afternoon.

Churches in the Denver area have changed their signs to honor the victims, and radio DJs have been reading messages of support. But inside the homes and hospital rooms where victims were recovering, the second day was said to be harder than the first. The adrenaline had worn off, leaving the reality of injury and loss.

It was the first full day of living with what happened, and what happened still didn’t make any sense.

Annie Dalton, the aunt of Ashley Moser, told the Associated Press that the critically wounded 25-year-old has been in and out of consciousness and had not been told that her daughter, Veronica, did not survive the shooting.

“All she’s asking about, of course, is her daughter,” Dalton said, according to AP. “She was a vibrant 6-year-old. She was excited, she’d just learned how to swim.”

The Navy and Air Force confirmed that John T. Larimer, 27, and Jesse Childress, 29, both stationed at Buckley Air Force Base in Aurora, had been killed.

“Sailors were really drawn to his calming demeanor and exceptional work ethic,” Cmdr. Jeffrey Jakuboski, Larimer’s commanding officer, said of the young petty officer. “He truly did have a bright future ahead of him in the Navy.”

Lt. Col. Pat Walsh, who supervised Childress in his job as a computer technician, said: “He literally touched everyone in the wing, over a thousand people. . . . We’ll get through this, but it’s extremely difficult for us right now.”

Matt McQuinn, 27, died at the theater trying to protect his girlfriend, Samantha Yowler, 27, along with her brother, Nick Yowler, 32. McQuinn and Nick Yowler stood up to shield Samantha from the bullets. McQuinn was struck in the chest, leg and back, said lawyer Rob Scott, a spokesman for both families. Samantha Yowler is in the hospital recovering from surgery after a bullet struck her knee.

Alex Sullivan of Aurora was at the midnight showing to celebrate his 27th birthday when he was killed.

“Alex is known for his bear hugs,” said his cousin Steve Schwab. “It doesn’t matter how long since you’ve spoken to him, he’ll always end the call with ‘I love you.’ ”

Sullivan, known for his love of comics, worked at the Aurora theater where he died. Sullivan’s family didn’t get confirmation of his death from authorities until Friday evening.

“What we just kept thinking is that he was in the theater helping everyone, because that would be his natural inclination,” Schwab said.

Three helicopters circled above the movie theater Saturday afternoon. The nearby mall was closed. Some cars from Thursday night’s premiere still sat behind police tape in the parking lot.

Down the block, mourners dropped flowers at a makeshift memorial on a street corner. Two men stood by the memorial and held up signs promoting Jesus — one in English, one in Spanish.

Achenbach and Farnam reported from Washington. Jenna Johnson and Carol D. Leonnig, in Washington and Eli Saslow and special correspondent Sandra Fish in Colorado contributed to this report.