Former medical student James Holmes was arrested after a masked gunman who burst into a midnight screening of the latest Batman movie and opened fire after first discharging a tear gas grenade.
After the shooting, police went to his apartment but found it filled with trip wires and chemicals, leading to the evacuation of five buildings nearby.
Cassidee Carlson of Aurora police, said security authorities from the local police and FBI, along with bomb disposal experts and firefighters, cleared the first trip wire and incendiary device.
She said: "We have been successsful in defeating the first threat.
"This trip wire was set up to clearly detonate when someone entered that apartment. It was set up to kill that person, and that could have been a police officer executing a search warrant or anyone.
"Now the team is reassessing the scene, now that first device has been dealt with.
"There are other devices inside. I am not going into detail about what they are."
Earlier she said that after the apartment had been made safe, incendiary items, including about 30 shells, would be placed in sand trucks and taken away a disposal site.
Bomb disposal expert Chris Hunter told Sky News: It suggests from what we know so far that there are multiple devices, what we call access denial devices, designed particulary to kill, maim or injure anybody physically trying to get access to the property.
"They are working on four priorities: preservation of life, preservation of property, preservation and collection of forensic evidence and returning the situation to normal as soon as possible."
Holmes is scheduled to appear in Courtroom 201 of the Arapahoe County Justice Center on Monday in front of Chief Judge William B. Sylvester.
Police have said Holmes legally bought four guns in local shops and 6,000 rounds of ammunition over the internet.
More to follow...