The events that played out in this Denver suburb on July 20 have shifted the course of many lives. The victims and their families will never be the same, of course. Nor will the University of Colorado's Anschutz Medical Campus, where James E. Holmes, 24, who is charged with killing 12 and wounding 58 at a midnight showing of the new Batman movie, was until June a graduate student. But for the doctors, nurses and other staff at the hospital—which received 23 of the injured, one of them dead on arrival—the shootings were not only a trauma but also a test of their skills, their stamina and their teamwork, as the simulated disaster drills they had practiced turned abruptly into reality.