AURORA, Colo. (Reuters) - The man accused in a shooting rampage at a Denver-area premiere of the new "Batman" film received a high volume of deliveries at work and home over the past four months, police said, parcels they believe contained ammunition and possibly bomb-making materials.
Aurora Police Chief Dan Oates revealed the shipments as local and federal authorities worked to make safe suspect James Holmes' apartment, which was found to be booby-trapped with sophisticated explosives following the massacre at a multiplex theater several miles away.
Oates said residents of nearby buildings who were evacuated would likely be allowed to return home on Saturday night.
"We've become aware that the suspect over the last four months received a high volume of deliveries to both his work and home addresses," Oates said at an afternoon press conference.
"This begins to explain how he got his hands on all the magazines and ammunition," Oates said. "We also think it begins to explain some of the materials he had in his apartment."
A gunman armed with an assault rifle, a shotgun and a pistol and wearing a full suit of tactical body armor, a helmet and a gas mask set off two smoke bombs before opening fire in the dark theater early on Friday morning, killing 12 people and injuring 58 others.
Officers who arrived at the scene within 90 seconds of the first emergency calls quickly took Holmes into custody in a parking lot behind the cinema, where he surrendered without a fight, Oates said.
Holmes, a graduate student who authorities said 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.
Authorities used a remote-controlled robot and controlled detonation on Saturday as they began to neutralize what they said were a series of booby traps in Holmes' apartment.
The bomb squad used a robot to place a tube -- known as a "water shot" -- near an explosive device in the apartment. The water shot was then detonated to disable the explosive.
Photos of the apartment, taken by a camera raised up to the third-floor window, showed jars of ammunition on the floor and "things that look like mortar rounds," Oates said.
There were also bottles filled with an unknown liquid and what appeared to be trip wires laid out across the apartment, he said.
Aurora Police spokeswoman Sergeant Cassidee Carlson said the device had clearly been "set up to kill."
"We have been successful in disabling a second triggering device," she said. "Although not certain, we are hopeful we have eliminated the remaining major threats. We will not know this until we enter the apartment."
Police evacuated five nearby buildings and created a perimeter of several blocks around Holmes' apartment, the top-floor unit of a three-story red brick building in a run-down section of Aurora.
Of the 58 people wounded in the shooting, hospital officials said some patients had sustained serious head injuries and chest injuries.
The University of Colorado Hospital, which treated 23 victims of the shooting, said 10 people had been released and five remained in critical condition.
The Medical Center of Aurora said of its seven patients -- ranging in age from 16 to 31 -- four remained in the intensive care unit and three other patients are on the main trauma floor.
"The initial adrenalin rush of having something like this happen, both for the families and the patients themselves, is starting to wear off," said Dr. Bob Snyder, a trauma surgeon at the Medical Center of Aurora. "There is going to be some realization that there are going to be some serious, long-term issues that people are going to have to deal with."
A memorial of flowers, candles and stuffed animals has been set up at the Aurora shopping mall where the shooting rampage took place. A handwritten sign read: "7/20 gone not forgotten."
President Barack Obama called the shootings a reminder that life is fragile and promised that the federal government stood ready to do all it could to seek justice for the "heinous crime.
"Even as we come to learn how this happened and who's responsible, we may never understand what leads anyone to terrorize their fellow human beings," Obama said in his weekly radio and Internet address, which was broadcast on Saturday.
Witnesses at the movie theater told of a horrific scene, with dazed victims bleeding from bullet wounds, spitting up blood and crying for help. Among those taken to hospitals as a precaution was a baby boy just a few months old.
"I slipped on some blood and landed on a lady. I shook her and said, 'We need to go; get up,' and there was no response, so I presumed she was dead," said Tanner Coon, 17.
The suspect may have blended in with other moviegoers who wore costumes as heroes and villains, and some witnesses said they believed at first that his appearance was a theatrical enhancement to the film.
The shooting 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.
The gunman was armed with an AR-15 assault rifle, a 12-gauge shotgun and a Glock .40-caliber handgun, Oates said. Police found an additional Glock .40-caliber handgun in his car, parked just outside the theater's rear emergency exit, he said.
Holmes had purchased the weapons legally at three area gun stores in the last 60 days and bought 6,000 rounds of ammunition online, including a 100-round drum magazine for an assault rifle, Oates said.
Additional reporting by Keith Coffman, Stephanie Simon and Dan Whitcomb; Writing by Edith Honan and Dan Whitcomb; Editing by Eric Beech and Stacey Joyce