RESUMEN
BACKGROUND: An active shooter in a hospital is an emergency extraordinaire. We report a single institution's response to the largest active shooter mass casualty event in American History. METHODS: Review of notification, flow of prioritized patients, and key elements of the day's dynamic after a hospital attack by a lone gunman were commenced. The review includes outcomes on seven victims and assailants. RESULTS: "Code Silver" announced: open display of a weapon. Concise, known, and published chain of command implemented. All house staff to the Emergency Department (ED) via text blast. Operating room (OR) notified. Injured to ED, then triaged to OR. Armed NYPD stationed throughout OR. Senior surgeons controlled key triage during attack with flow controlled from the ED and OR control desk. One fatality plus shooter. CONCLUSION: Success favors the prepared. The response to attack, readiness of medical personnel, mitigation, and recovery have brought the following recommendations: (1) single entrance access; (2) armed, professional guards at all entrances; (3) camouflage metal detectors; (4) mandatory, recurrent hospital-wide active shooter training, mock, and table top; (5) published physician chain of command; (6) intercom code system known to all hospital personnel indicating a weapon is openly displayed; (7) a "no fly" list of former employees who are prohibited on premises; (8) stop the bleed training with kits on every floor; (9) one voice, one face to disseminate information. LEVEL OF EVIDENCE: Prognostic and Epidemiological; Level I.