By Alyssa Newcomb and Lauren Effronf, ABC News
Authorities in Colorado today outlined a plan to disarm and enter the booby-trapped apartment of a man who is accused of perpetrating the largest mass shooting in U.S. history, in hopes of finding a motive for the deadly rampage.
A large number of explosive devices and trip wires were found at the apartment of James Holmes in an "elaborate" set-up, said Aurora Police Chief Dan Oates.
Some devices appeared to be strapped to boxes of bullets and what looked like mortar rounds, police said.
"We don't need to rush anything and we're going to do our best to just take our time to keep it as safe as possible," said Cassidee Carlson, spokesperson for the Aurora Police Department.
Authorities have established a three step plan for entering the apartment that may include controlled detonations, which may "cause a lot of boom" and potentially a fire, Carlson said.
The "flammable and explosive" materials could have blown up Holmes' apartment building and the ones near it, police said.
One official told ABC News that there were wires everywhere and described Holmes as a like a mad scientist.
Once the trip wires are disarmed, authorities will then dispose of the incendiary devices in the apartment, including approximately 30 aerial shells, which will be placed into sand trucks and taken to a disposal site, Carlson said.
From that point, police plan to move into the investigation phase, hoping Holmes' computer and any writings could provide a gateway to understanding his motive.
A former doctoral student, Holmes, 24, is suspected of killing 12 people at the screening of the latest Batman movie in Aurora, Colorado early Friday morning. Fifty-eight people were wounded.
According to police sources, Holmes, told the officers arresting him that he was "The Joker," referring to the villain in the second installment of the Batman movie trilogy, "The Dark Knight." He also warned police that he had booby-trapped his apartment, leading officers to evacuate the Aurora apartment building.
Authorities said there is widespread concern over copy cats and police in New York City, Washington, D.C., and other jurisdictions have stepped up their securities.
Two other people died at the hospital, including 24-year-old aspiring sportscaster Jessica Ghawi. Police said thirty people remained hospitalized with 11 of them in critical condition. Bullets from the shooting spree tore through the theater and into adjoining theaters, where at least one other person was struck and injured.
Authorities said they have finished the grim task of identifying the 10 victims who were killed inside the theater when Holmes allegedly opened fire during the midnight premiere of "The Dark Knight Rises," and are now going door-to-door to notifiy families.
Among the dead include Micayla Medek, 23, Alex Sullivan, 27, who was attending the movie for his birthday, Ohio native Matt McQuinn and Alex Teves, 24.
John Larimer, a member of the U.S. Navy, was also confirmed by his family to be among the dead.The family said they were notified at their Illinois home around mignight today by a Navy notification team that Larimer was dead.
Chief Oates announced Friday that Holmes had purchased four guns at local shops and more than 6,000 rounds of ammunition on the Internet in the past 60 days.
"All the ammunition he possessed, he possessed legally, all the weapons he possessed, he possessed legally, all the clips he possessed, he possessed legally," an emotional Oates told reporters at a press conference.
The chief declined to say whether the weapons were automatic or semi-automatic, but "he could have gotten off 50 to 60 rounds, even if it was semi-automatic, within one minute," Oates said.
Eyewitness and victim accounts of the mass shooting that took place inside of a packed movie theater in Aurora, Colo., Friday morning continue to paint a picture of panic and horror.
Eric Hunter said this morning that he was in an adjacent theater to where the shooting took place, when bullets "came right through the walls."
"When the first three shots rang out, we didn't know if it was part of the movie or not," he said. "I saw blood on the stairs and I turned to the crowd and said there's something wrong and we need to call the cops."
Hunter then said he made his way to the emergency exit door, where he saw two teen girls outside, one of whom had been hit by bullet and was asking for help. Thats when Hunter said he saw the shooter.
"I saw the gunman coming around the corner so I held the door for about five seconds," Hunter said. "He's banging on the door, banging on the door...I didn't know if he was going to shoot the door. I didn't know what he had."
Holmes allegedly entered the movie auditorium wearing a ballistics helmet, bulletproof vest, bulletproof leggings, gas mask and gloves. He detonated multiple smoke bombs, and then began firing at viewers in the sold-out auditorium, police said Friday.
Holmes, who is being held in jail and will make his first court appearance Monday, is originally from Riverside, Calif., where he attended the University of California branch, Oates said Friday.
"Neighbors report that he lived alone and kept to himself," he added.
Holmes was apprehended within minutes of the 12:39 a.m. shooting at his car behind the theater, where police found him in full riot gear and carrying three weapons, including an AR-15 assault rifle, which can hold upwards of 100 rounds, a Remington 12-gauge shotgun, and a .40 Glock handgun. A fourth handgun was found in the vehicle.
Agents from the federal bureau of Alcohol, Tobacco, and Firearms are tracing the weapons.
ABC News' Brian Ross and Pierre Thomas contributed to this report.