The University of Colorado said Sunday it was investigating whether mass shooting suspect James Holmes used his position as a graduate student to order materials in the potentially deadly booby traps that police said they found in his apartment. Holmes, 24, received deliveries to his home and school over a period of four months, authorities have said. The university is looking into what was sent to the school to assist police with their investigation, said spokeswoman Jacque Montgomery. The suspect was described as a budding scientist, brimming with potential, who pursued a graduate program even as he planned the attack with “calculation and deliberation,” police said. Investigators spent hours Saturday removing explosive materials from inside Holmes’ apartment a day after police said he opened fire and set off gas canisters in a movie theater minutes into a midnight screening of the “The Dark Knight Rises.” The massacre left 12 people dead and 58 wounded. His apartment was booby-trapped with jars of liquids, explosives and chemicals that could have killed “whoever entered it,” Aurora Police Chief Dan Oates said, noting it would have likely been one of his officers. Inside the apartment, bomb technicians neutralized a “hypergolic mixture” and an improvised explosive device containing an unknown substance, said James Yacone, an FBI special agent. There were also containers of accelerants, creating “an extremely dangerous environment,” he said. Oates said on CBS television’s “Face the Nation” that he had never seen a booby trap as elaborate as what was found in the apartment. By late Saturday afternoon, all hazards had been removed from the apartment and residents in surrounding buildings were allowed to return home, police said. Police left the apartment building carrying a laptop computer and a hard drive around 8 p.m. Saturday. Holmes was in solitary confinement for his protection at a Denver-area county detention facility, held without bond on suspicion of multiple counts of first-degree murder. He was set for an initial hearing Monday and has been appointed a public defender. President Barack Obama traveled to Colorado Sunday to visit the families of victims. New York Mayor Michael Bloomberg – one of the few high-ranking U.S. politicians that openly favors gun control – demanded Sunday that both Obama and his Republican presidential rival, Mitt Romney, take action on gun control. “This really is an enormous problem for the country, and it’s up to these two presidential candidates. They want to lead this country, and they’ve said things before that they’re in favor of banning things like assault weapons,” Bloomberg said on “Face the Nation.” “Where are they now and why don’t they stand up?” asked Bloomberg. “If they want our votes, they’d better.”