Department of Homeland Security Quick Reference Guide (PDF) here: https://www.cisa.gov/sites/default/files/publications/active-shooter-pamphlet-2017-508.pdf

DHS informational links and videos can be found here:  https://www.cisa.gov/active-shooter-preparedness

FBI ASAPP (Active Shooter Attack Prevention & Preparedness) Resources: https://www.fbi.gov/how-we-can-help-you/active-shooter-safety-resources/active-shooter-attack-prevention-and-preparedness-asapp

Active Shooter Event Quick Reference (English): https://www.fbi.gov/file-repository/active-shooter-event-quick-reference-guide_2015.pdf/view

Active Shooter Event Quick Reference (Spanish): https://www.fbi.gov/file-repository/active-shooter-event-quick-reference-guide-spanish1.pdf/view