The suspect in last week's deadly shooting rampage at a crowded Colorado movie theater boobytrapped his apartment with more than 30 homemade grenades and 10 gallons of gasoline.
The sophisticated set up at the sparsely furnished Aurora home of James E. Holmes was meant to harm, or possibly kill, anyone who entered -- and tested the skills of bomb squad members charged with clearing it.
"Imagine that fireball ... you would have an explosion that would knock down the wall of (nearby) apartments," the official said. "That flame would have consumed the entire third floor (of the apartment complex)."
"By the time a fire truck would have arrived, they would have arrived to a building that would have been completely consumed in flames."
The grenades were wired to a control box in the kitchen, which bomb technicians disabled with the help of a remote-controlled robot that squirted water on it.
"It looked like spaghetti," according to the official, who said it resembled setups that are used in Iraq and Afghanistan, but rarely in the United States.
The control box has been sent to Quantico, Virginia, for forensic analysis at the FBI laboratory, the official said.
But the setup appears to have been "rigged" so that it would have exploded, according to the official. A "post-blast analysis" will determine if it would have worked.
The gasoline was divvied up into glass containers and gas cans in order to "enhance the thermal effect of the explosion," the official said.
Over the weekend, Aurora Police Chief Daniel Oates told reporters there was "evidence of ... some calculation and deliberation" in the Friday attack at the Century Aurora 16 multiplex.
Holmes received deliveries over the past four months at his home and work addresses, which begins to explain how he may have obtained some of the materials used in the attack and those found at his apartment, Oates said.
Holmes is being held in connection with the shootings that killed 12 people and left 58 others wounded. As of late Monday, at least 15 people remained hospitalized -- five in critical condition -- in four area hospitals.