Following  over ten years of active shooter response protocol development and training,  when James Holmes attacked a theater full of people in Aurora, Colorado, the  response from local and surrounding agencies, not to mention the response of  emergency medical personnel, was near picture perfect. The audio tapes that  were temporarily released of the law enforcement communications revealed  officers who sounded near panic and other officers who sounded like they had  responded to a hundred such attacks before; very calm, cool, collected and in  control. 
No  more or less should be expected when a lone gunman walks into a crowded  theater, throws OC grenades and then begins shooting with (reportedly) multiple  firearms. With a total of 12 people killed and 70 more wounded, Holmes was  determined to be the sole assailant. He was arrested after being found in his  car behind the theater just a few minutes after the shooting ended. The following  day, when a search warrant was served on his apartment, it was discovered to be  booby-trapped with improvised explosives that had to be dealt with by the bomb  squad before the apartment could be searched.   This is yet another example of an attacker using explosives either in  combination with weapons to commit the attack OR as a secondary threat to cause  more casualties after the initial attack has been completed.
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The remainder of this article is part of the book "Active Killers and the Crimes They Perpetrated," available in print or ebook via Amazon.