He then returned to the theater two days later to take pictures of exterior doorways, Fyles testified.

The apartment

Witnesses detailed preparations that prosecutors believe Holmes made before setting out for the theater to turn his sparsely decorated Aurora apartment into a deathtrap.

At least some of the preparations were well under way by July 16, based on a photograph from Holmes' phone shown by prosecutors. In it, jars, wires, firework shells and other bomb-making materials are laid out in his kitchen.

By the time Holmes left, the carpet in his apartment had been soaked in oil and gas, FBI bomb technician Garrett Gumbinner testified. A container of glycerin hung above a frying pan with a potassium mixture, attached to a trip wire that would tip the glycerin into the pan, Gumbinner testified.

If triggered, Gumbinner said it would have set off an explosion and fire, igniting jars of homemade napalm spiked with bullets and thermite -- a metallic substance that burns so hot it is nearly impossible to extinguish.

In a diabolical twist that seems ripped from the pages of a comic book, witnesses said Holmes also rigged his computer and a boom box placed outside to begin playing loud music after he set out for the theater -- apparently in hopes that the noise would prompt someone to investigate and trigger the explosives.

Next to the boom box outside his apartment, Gumbinner testified, Holmes said he placed a toy car and a device that looked like it would control the car but would in fact set off the explosives.

Authorities recovered the boom box, bearing Holmes' fingerprints. The remote-control car device was never found, Appel testified.

A series of disturbing self-portraits displayed in court, apparently made sometime before Holmes allegedly left for the theater, according to data retrieved from his phone, show him in the eye-blackening contacts, his tongue stuck out in one, flashing a toothy grin and a handgun in another.

The shooting

Video from the theater shows a man they say is Holmes -- wearing dark pants, a light-colored shirt and a dark stocking cap covering his orange hair -- entering the multiplex before the movie begins.

The recordings show him going into Theater No. 9, a different theater from the one listed on his ticket.

While witnesses have not detailed in this week's preliminary hearing what investigators believe Holmes did once inside the theater, sources have said they believe he propped open the theater's back door and went to his car to put on body armor and arm himself. Authorities believe Holmes then re-entered the theater, tossing gas canisters before opening fire about 18 minutes into the movie, according to sources.

Witnesses who have spoken to CNN about the shooting have said the gunman roamed the theater, shooting people randomly as they tried to scramble away or cowered between seats.

Among the 41 calls to 911, one stands out. In the 27-second call, the sounds of at least 30 shots ring out amid the chaos.

At some point, according to Pearson, one of Holmes' weapons jammed.

"Had the AR-15 not jammed, he would have killed more people," she said.

Investigators found 76 shell casings in the auditorium. Most of the spent rounds -- 65 -- were .223 caliber rifle rounds, six were shotgun shells and five were .40 caliber rounds from the Glocks, Appel said. Police also found one of the tear-gas canisters inside the theater, Appel said.

Also located was a large drum magazine for the rifle that appeared to have jammed, Sgt. Gerald Jonsgaard testified Monday.

The rifle cartridges were steel-core rounds, which are more likely to pass through a body intact and can cause multiple wounds, Fyles testified.

The movie theater's video system didn't capture anything from inside the theater but did capture the aftermath -- streams of terrified patrons running from the theater.

On Monday, police who were first to arrive described an eerie scene, stepping into a movie theater with "Batman" still blaring from the screen, blood from badly wounded victims flowing in the aisles and cell phones ringing over and over again, without answer.

Outside, the first officer to encounter Holmes -- who was still dressed in body armor, a helmet and a gas mask as he stood near his car -- described him as unnaturally relaxed. In fact, from Holmes' appearance, Officer Jason Oviatt thought he was a fellow police officer.

A trail of blood led from the theater. The rifle that authorities believe Holmes used in the attack lay on the ground near the building. Holmes was just standing there, Oviatt testified Monday.