During his arrest the 24-year-old shooting suspect told police he had booby-trapped his third-floor apartment, prompting investigators to evacuate the building and four others nearby.
Authorities spent Friday and Saturday trying to disarm possible explosives and collecting various materials, like some 30 softball-sized containers filled with gunpowder that were found in Holmes' apartment.
Ret. FBI Agent and explosive expert Ray Lopez says, “It could have been much worse had [the police] not been able to get inside the apartment and identify those chemicals and the other components they found in there."
Lopez says Holmes probably went on the internet to learn how to create and put various parts of his booby-trap together but it really boiled down to “his motive, his ability to get these components and his education.”