The Aurora shooting spree is one of the deadliest in U.S. history--and authorities believe it was the work of only one man.
"All the evidence we have, every single indicator is that...he wasn't particularly aided by anyone else," Police Chief Dan Oates said Sunday. "We're building a case to show that this was a deliberative process by a very intelligent man who wanted to do this."
Police have also learned that over a span of a few months, suspect James Holmes received a number of packages in the mail, believed to have contained the tools used to gun down dozens of innocent people--and turn his home into a potential killing machine.
"He had a high volume of deliveries," Oates said. "We think this explains how he got his hands on the magazine, ammunition." Oates said it was presumably how Holmes got his hands on the astonishing number of explosives he rigged in his home.
The complex system of booby traps proved "vexing" for authorities in Aurora as they contemplated how to gain access into shooting suspect James Holmes' residence.
After more than 24 hours, authorities were finally able to detonate the extensive series of trip wires strewn across Holmes' apartment, as well as at least one explosive device. The Aurora Police Department says the detonation was successful; shutters rustled when the explosives went off, but no fire erupted.
Authorities were able to remove all dangerous explosives from the apartment by Saturday night, allowing most evacuated residents to return home--thought the ones living inside Holmes' building are still evacuated as of Monday morning. The explosives are being shipped to an FBI lab.
Officials say that besides the grenades, the apartment had two other types of explosives: jars filled with accelerants and chemicals intended to explode when mixed together.
Holmes alluded to having explosives inside his apartment upon his arrest, but authorities say what they found after placing a camera inside was stunning.
"I have never seen anything like what the pictures show us in there," Aurora Police Chief Dan Oates said.
According to CBS News, Holmes, 24, may have booby-trapped his apartment in hopes of luring officers away from the bloody scene at the Century 16 movie theater, where he is suspected of gunning down a crowd of movie-goers at "The Dark Knight Rises" premiere just after midnight Friday. Seventy people were injured in the shooting; 12 have been confirmed dead.
Holmes reportedly had loud music blaring around the time of the shooting spree to provoke neighbors into calling in a noise complaint, thus bringing officers to his home, setting off an explosion and diverting resources from the movie theater.
After disarming the wires and the first explosive device, Aurora Police Sgt. Cassidee Carlson said that the booby trap was rigged to kill the first person to walk through the door.
Neighbor Kaitlyn Fonzi could have been that person. Fonzi told CNN she came so close to opening Holmes' door Thursday night that she actually her hand on the doorknob.
The loud music had drawn Fonzi to his apartment, just as authorities speculate he intended.
Though the door felt unlocked, Fonzi abruptly changed her mind about going inside.
"I yelled out and told him I was going to call the cops, and went back to my apartment," Fonzi said.
Arresting Holmes was the simplest part of the investigation process; responding officers were on scene within a minute and immediately found Holmes behind the theater.
It was upon arriving at his home that authorities reached a temporary standstill.
"I'm a layman when it comes to bomb stuff, [but] I see an awful lot of wires, trip wires, jars full of ammunition ... jars full of liquids, mortar rounds. We have a lot of challenges to get in there safely," Oates said Friday.
Entering the apartment Saturday was considered extremely dangerous, particularly if Holmes, a former neuroscience PhD student who was "top of the top" academically while an undergraduate science student, was skilled at setting the explosive devices. Bomb technicians entered the apartment in full protective gear. One hundred personnel, including the bomb techs, firefighters, ATF and FBI were on scene Saturday.
Officials say technicians first used a robot to remotely remove trip wires, then move inside the 800 square foot apartment to detonate the improvised devices.
Aurora police said in a press conference Friday that Holmes has no previous criminal history in Aurora outside of a traffic violation. 11 News has looked at court documents for the state of Colorado, and have been unable to find any indications of a prior criminal background in the state.
CBS says Holmes, originally of San Diego, doesn't appear to have a criminal record in California either.
The CBS affiliate in San Diego, KFMB, reports that Holmes' mother lives in the Rancho Penasquitos suburb of that California city. The family has issued a short statement: "Our hearts go out to those involved in this tragedy, and to the families and friends of those involved."