FBI Details James Holmes' Elaborate Booby-Trap Also: Holmes played sock puppets with paper bags on his hands By John Johnson, Newser Staff Posted Jan 8, 2013 5:06 PM CST 17 comments Comments This courtroom sketch shows James Holmes being escorted by a deputy as he arrives at preliminary hearing in district court in Centennial, Colo., on Monday. (AP Photo/Bill Robles, Pool) (Newser) – An FBI agent today laid out the meticulous detail used by James Holmes to booby-trap his apartment on the night of the Dark Knight massacre in Aurora, Colorado, reports USA Today. According to his plan, a boombox would start blaring in the empty apartment at midnight. When neighbors or police knocked on his door, that would jostle a fishing line and set things in motion, as the Denver Post explains: "The line would topple the thermos full of glycerin, and the glycerin would mix in the frying pan with the potassium permanganate to create a flame. The flame would set the petroleum-soaked carpet on fire. The fire would light the fuses. The fuses would detonate the jars filled with homemade thermite, smokeless powder and stove-top napalm mixed with bullets." What's more, Holmes had a second system in place to cause even more destruction, apparently hoping to lure police resources from the theater. "The whole apartment would have either exploded or caught fire," said the FBI agent. The only reason it didn't is because Holmes' neighbors didn't make a fuss about the loud music. Also today: The court heard a 911 call from a sobbing 13-year-old, cousin of the youngest person killed, Veronica Moser-Sullivan. A dispatcher tried to tell the teen how to perform CPR, but the girl couldn't hear over the noise in the theater. A police detective said that after authorities put paper bags over Holmes' hands to preserve evidence, he started playing with them as if they were sock puppets, reports AP. He also tried to jam a staple into an electrical outlet. An officer on the scene said Holmes seemed "very, very relaxed." When the officer asked whether Holmes had help with the massacre, "he just looked at me and smiled ... like a smirk."