The U.S. Department of Homeland Security has published to its Active Shooter Preparedness website four new active assailant guides to provide the critical infrastructure community with information regarding attack vectors used by terrorists and other extremist actors as well as corresponding suggested protective measures. The four new guides specifically address chemical attacks, active shooter attacks, vehicle rammings, and security for mass gatherings. Each provides a series of scenarios for how an attack might take place, includes indicators of an attack that’s about to happen or is in progress, and lists recommended measures to respond and mitigate impacts. DHS.