(CNN) -- The suburban Denver community of Aurora grappled Saturday with how to emerge from the chaos and carnage that ripped the city early Friday, when a masked man dressed in black went on a shooting spree inside a movie theater.

"It is going to be a long day for a lot of people," said Dr. Bob Snyder, a trauma surgeon at Aurora Medical Center, where 18 victims were taken after the shootings. By Saturday, seven remained, two of them in critical condition. "The adrenalin rush of having something like this happen, both for the families and the patients themselves, is starting to wear off."

Grief counselors were staffing area high schools Saturday. The city is planning a vigil Sunday night.

And investigators were making headway toward entering the booby-trapped apartment of shooting suspect James E. Holmes, a 24-year-old Ph.D. candidate in neuroscience.

"We have been successful in defeating the first threat, a trip wire," Sgt. Cassidee Carlson told reporters. "This trip wire was set up to clearly detonate when somebody entered the apartment, and it was set up to kill that person."

They also dealt with an incendiary device, she said. Later, authorities carried out a controlled detonation inside the apartment. A policeman yelled, "Fire in the hole!" three times and then a boom was heard.

"There are other devices inside," Carlson said.

Hundreds of residents remained evacuated Saturday from five buildings, including the modest, three-story brick building where Holmes told police he had rigged his top-floor, one-bedroom apartment with explosives.

Investigators have said little about what may have led the suspect to kill 12 people and wound 58 others during a premiere Friday of the Batman sequel "The Dark Knight Rises."

As the identities of those who died were becoming public Saturday, Town Center at Aurora reopened for business, though its movie house -- Century Aurora 16 -- remained shuttered.

The incident began unfolding late Thursday, when Holmes bought a ticket to the midnight show and entered the Century Aurora 16 theater, a law enforcement source involved in the investigation told CNN.

The sold-out theater was filled with Batman fans, some in costume.

But Holmes soon went out a rear door leading from the theater to the parking lot, leaving it propped open, the source said. He gathered weapons before re-entering through the same door, said the source, who was not authorized to release the information.

He was back inside the theater a few minutes after the movie had begun and was dressed head-to-toe in black, authorities said.

Witnesses described him as wearing a gas mask that concealed much of his face and head.

Oates declined to release details about Holmes' appearance other than to describe what he was wearing: a ballistic helmet and protective gear for his legs, throat and groin, black gloves and a gas mask.

He said he would not release the booking photo "for investigative reasons."

Police said Holmes set off two gas-emitting devices before spraying the theater with bullets from an AR-15 rifle, a 12-gauge shotgun and at least one of two .40-caliber handguns that police recovered.

Holmes had bought the guns legally at stores in the Denver area over the past two months, Oates said.

More than 6,000 rounds of ammunition were also purchased online, Oates said.

A receipt obtained by CNN shows Holmes bought some of the tactical gear, including a vest and a magazine pouch, online on July 2.

Holmes surrendered without resistance within seven minutes of the first 911 calls from moviegoers, Oates said. He was arrested in the theater's rear parking lot.

Holmes' hair had been dyed red, and he told police he was "the Joker," according to a federal law enforcement source with knowledge of the investigation. The source was not authorized to release details to the media.

The federal law enforcement source's information about the suspect's appearance fits with a statement made to reporters by New York Police Commissioner Ray Kelly, who said he had been briefed by Colorado authorities.

In all, 10 people were killed inside the theater; their bodies were removed by Friday night and authorities started "the agonizing process" of notifying families, Oates said. Two of the gunshot victims died in hospitals.

Witness: 'Longest minute of my life'

The Joker has long been a fixture in Batman comics and was famously portrayed by Heath Ledger in 2008's "The Dark Knight," the predecessor to "The Dark Knight Rises." Ledger, who died in 2008, won a posthumous Academy Award for his portrayal of the villain who encourages anarchists to take over Gotham City.

On Saturday, 19 victims remained hospitalized -- two in critical condition -- in five hospitals.

Holmes, who is being held in Arapahoe County Jail, is scheduled to appear in court on Monday morning. The court file was sealed, according to a court order.

A statement from Holmes' family in San Diego asked for "privacy during this difficult time."

"Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved," the statement said. "We are still trying to process this information."

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CNN's Carol Cratty, Ed Lavandera, Susan Candiotti, Joe Sutton, Mike Brooks, Sarah Aarthun and Jim Spellman contributed to this report.