"In this dynamic threat environment, it is important that organizations not only prepare their staff to respond to a potential incident, but also collectively determine the processes through which the organization and its staff recover from an incident. Incidents such as mass shootings at Pulse Nightclub in Orlando, FL on June 12, 2016, and at an office holiday party in San Bernardino, CA on December 2, 2015, have demonstrated acts of violence such as active shooter incidents, can happen anywhere. Threats may be either external or internal. Although appropriate measures should be taken to protect an organization from a potential attack, it is nearly impossible to completely prevent every incident. As such, if an active shooter event or other attack occurs, it is vital that organizations prepare themselves to effectively recover, taking into consideration the business and human elements."
Department of Homeland Security: https://www.dhs.gov/