Active shooter incidents have been on the rise in the United States in the last 2 decades, specifically events occurring in public areas traditionally considered safe such as churches, schools, and hospitals. An examination of historical events shows that the emergency department (ED) nurse must be equipped to handle any situation that may arise, including the increasing likelihood of an active shooter situation. Hospital response to these occurrences is changing, and protocols for staff response are being adjusted on a regular basis. Immediate response, postevent actions, and evidence collection procedures must be a part of the ED nurses' ongoing education. Lessons learned from events that have occurred must be examined so ED nurses can be more aware and ready to respond to the increasing chance of an event such as this occurring in their ED.