Civil unrest or terrorism at mass gathering events can erupt with significant violence and multiple casualties. These are high-risk situations, not only because of physical casualties, but also because of ethical, political and psychological sequelae. Beyond specialized planning, multi-agency drills and proficient tactical medicine training, medical teams should co-create secured access and egress, alternative medical responses and rapidly-adapting coordination and secure communications with other agencies. Civil protests can escalate, especially when extremist groups infiltrate them. Multi-site violence and assaults can evolve, particularly in terroristic attacks. Key lessons include unrelenting vigilance until all participants have left the mass gathering scene in its entirety. Violence (bombs, shootings, vehicle attacks) will often erupt when mass gatherings are dispersing and considered over. Terrorists can also purposely target medical personnel or incite one event (fire, bomb, shooting) to create crushing stampedes or to herd crowds into more vulnerable areas where they can be further attacked more directly with other modern weapons. Terrorists often attack from elevated perches or generate “protracted suicide” incidents while holding hostages, including many severely-wounded. The resulting frustration, anger and guilt commonly can consume medical rescuers when beholding slaughtered innocents or simply because they were (appropriately) staged during containment of on-going violence.