Taking a one-word lesson from modern active shooter response protocols to tackle problems you cannot neglect: Engagement. Some foundational ideas behind this have been around quite a while, as in here: US Department of Homeland Security Active Shooter Pocket Card. Center for Personal
Protection & Safety Active Shooter Regional Training Seminar 2010. "Active Shooter in the Workplace" course sponsored in 2010 by the
Orange County PSTRG. "Active Shooter in a High-Rise Building" training on 4/28/10 sponsored by LAPD SWAT, LAPD Metro Division, and Downtown Security Managers' Association.