Autrey, A., Hick, J., Bramer, K., et al. (2014). 3 Echo: Concept of Operations for Early Care and Evacuation of Victims of Mass Violence. (Abstract only.) Prehospital Disaster Medicine. 29(4):421-8.
The authors describe a three-phase approach used by responders to a mass shooting event that happened in Minneapolis (MN) in 2012: Enter, Evaluate, and Evacuate (or 3 Echo). 3 Echo stresses early, multi-disciplinary coordination and teaches participants about unified command, swift victim evacuation, how to establish corridors of safety, and other critical skills.