AURORA, Colo.- The man accused in a shooting rampage at a Denver-area premiere of the new Batman film received a high volume of deliveries in recent months, police said on Saturday, parcels they believe contained ammunition and bomb-making materials and showed evidence of "calculation and deliberation."

Aurora Police Chief Dan Oates discussed the shipments as local and federal authorities completed the painstaking process of disarming suspect James Holmes' apartment, which was found booby-trapped with explosive devices following the shooting massacre at a multiplex theater several miles away.

James Holmes, 24, is seen in this undated handout picture released by The University of Colorado July 20, 2012. [Photo/Agencies]

On Saturday afternoon, the local coroner's officer released the names of the 12 people killed. The victims ranged in age from 6 to 51. Most were in their 20s.

Aurora Police Chief Dan Oates said, "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. This begins to explain how he got his hands on all the magazines and ammunition.

"We also think it begins to explain some of the materials he had in his apartment," Oates said. "What we're seeing here is evidence of some calculation and deliberation."

Bomb experts used a remote-controlled robot to enter Holmes' apartment in Aurora and disabled two trip wires connected to a series of 30 improvised explosives that authorities said would likely have blown up the entire three-storey apartment building.

By late Saturday afternoon, police had removed the last of the devices, packed them in sand in a dump truck and drove them away, a law enforcement source familiar with the matter said.

Authorities said they were working carefully to preserve any evidence in the apartment, which could shed light on the motives for a crime that stunned Aurora and much of the nation.

A gunman wearing a full suit of tactical body armor, helmet and gas mask opened fire at a packed midnight showing of The Dark Knight Rises early on Friday morning, killing 12 people and wounding 58.

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, Oates said. Police found an additional Glock 40-caliber handgun in his car, parked just outside the theater's rear emergency exit, he said.

Police 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.

A poster for the Warner Bros. film "The Dark Knight Rises" is displayed at Warner Bros. studios in Burbank, California, July 20, 2012. [Photo/Agencies]

Arapahoe County Sheriff Grayson Robinson said Holmes was being held in solitary confinement to protect him from other prisoners, a routine move in high-profile cases.

Holmes, a 24-year-old 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.