It is a small three-storey red brick apartment building. Air conditioners are perched below windows adorned with potted flowers. And behind one of those windows this weekend: An intricate web of wiring and containers that formed an elaborate network of explosives and other devices believed to be designed by James Holmes, the man suspected of killing 12 in an Aurora, Colo., theatre.
Over the weekend, U.S. law enforcement officers deactivated most of the dangerous elements in the booby-trapped 800-square-foot apartment. The bombs were designed to erupt when the front door was opened, and had the devices been set off as anticipated, there is a strong likelihood they would have killed a police officer or firefighter sent to the scene. “If you think we’re angry, we sure as hell are angry,” Aurora police chief Daniel Oates said.
But undoing the potential danger was not simple. Firefighters were standing by in case the apartment went up in flames. Evidence was removed at each step in case an explosion erupted. This was “an extremely dangerous environment” that was “certainly challenging for all involved,” said Jim Yacone, the special agent in charge for the Federal Bureau of Investigation, who called the joint bomb squad’s efforts “heroic.”
How: To assess the apartment, officials used a cherry picker to break an outside window, and held inside a pole and camera to peer around. A robot was used to deactivate a tripwire attached to the front entry door. Then the work of dismantling the network began, starting with the deactivation of a “hypergolic mixture,” a type of chemical combination used in rocket engines with two substances that spontaneously combust when they come in contact. A triggering mechanism on an improved explosive device came next, followed by multiple containers with accelerants. At one point, officials used a “water shot,” which involves exploding a small amount of water into a device to neutralize it. Larger devices and fuel from inside the apartment were removed in a dump truck filled with sand and detonated off site.
What: Some 30 soft-ball sized devices were found; police also described seeing objects that looked like military mortar rounds. Many of the devices were jars containing a combination of incendiary substances, designed to unleash fire, and explosives. Officials declined to describe which specific substances were used, saying definitive analysis will be done at the FBI’s Terrorist Explosive Device Analytical Center laboratory in Quantico, Va, which has experience assessing more than 70,000 of what are called “submissions” from bombs used in places like Iraq and Afghanistan.
Who: The tremendous resources used at the apartment offer a window into the complicated nature of the operation. Numerous experts responded from the FBI; the Bureau of Alcohol, Tobacco, Firearms and Explosives; the Adams County Sheriff’s office; multiple police departments and the local Aurora fire department. Among the fields of expertise called upon: explosive samplers, chemists, device examiners, senior scientists, postblast recovery experts, explosive operation specialists, also known as bomb techs, and evidence-response recovery personnel.