Booby-trapped: 'Sapper' robot explores Colorado theater shooter's mine-studded home (POLICE VIDEO)

Newly-revealed video depicts a bomb squad robot entering the Aurora cinema shooter's apartment, rigged with explosives and incendiaries, three years ago. James Holmes killed 12 people and injured over 70 in a rampage at a Colorado theater in July 2012.

The video and photos have been released by the Arapahoe County District Attorney’s Office after open-records requests.

Multiple homemade explosive devices could be seen placed around the room, all connected with electric wires. The bombs are made of glass jars filled with gunpowder, rifle ammo and thermite. Dozens of wired black plastic spheres appear to be stuffed with a similar explosive cocktail.

Plastic bottles with flammable fluids are strewn about the floor, which is stained with gasoline and motor oil. Several 2-liter soda bottles placed in the back of the apartment were also filled with gasoline.

Holmes set several booby traps inside his apartment. The first one was a trip-wire consisting of a fishing line attached to the door jamb at one end and a thermos full of pure glycerin, positioned unstably on a frying pan that contained the chemical potassium permanganate.

READ MORE: Red-haired Joker: Colorado shooter James Holmes' first court appearance

When somebody opened the door, the thermos was supposed to fall and pour glycerin into the pan, when a chemical reaction would cause a huge flame “blowing up the whole apartment,” the ABC cited Richard Orman, a senior deputy district attorney for the 18th Judicial District of Colorado.

To make this happen, the shooter put a specially-prepared recording on ‘play’ before leaving, consisting of 40 minutes of silence and then a loud piece of music. Holmes apprently expected that one of his apartment neighbors would be disturbed by the loud music, come knocking at his door and enter the apartment. He’d left the door unlocked, and the entry would set off the tripwire, causing flames and an explosion.

He wanted this to happen to divert the attention of first responders before he began his attack in the theater, Orman said.

The explosion never happened, although Holmes’ downstairs neighbor Kaitlyn Fonzi did came to his apartment around midnight disturbed by the loud music. She knocked on the door, but since no one answered she left – saving her life.

Two more booby-traps set by Holmes were interconnected with a button inside the apartment and a remote control placed next to an toy car.

“We believe he hoped someone would hear the boom box, try to play with the car and use a remote control that would actually blow the whole place up,” Osman said.

In the end, none of the traps went off and were safely disarmed, though five buildings surrounding Holmes' residence had to be evacuated in the process.

Dressed in full body armor and armed with three guns, James Holmes killed 12 people and injured more than 70 others on July 20 at a movie theater in Aurora, Colorado, during a midnight screening of the Batman film ‘The Dark Knight Rises’.

He was apprehended immediately after the rampage behind the theater, telling police about the explosives in his apartment.

After a four-month trial, Holmes was sentenced to life in prison without parole in August.