On October 10, 2019, the Loudoun County Sheriff's Office (LCSO) and Loudoun County Fire and Rescue (LCFR) led one of the largest act of violence (AVI) exercises ever conducted in Loudoun County, Virginia. Over 300 participants and 50 role-players participated across 15 county departments and agencies within Loudoun County. The exercise identified an important recommendation: "future joint unified command trainings are needed throughout the fire and law enforcement command structures." Effective, unified command is an essential NFPA 3000 principle of responding to an AVI. "The success or failure of the response will hinge on the quality of unified command." After-action reports from AVIs across the United States emphasized the importance of unified command. A second exercise recommendation proposed "a joint AVI unified command competency scenario between LCFR and LCSO should be developed and delivered across all levels of supervision... this scenario should demonstrate 'best practices' for establishing and operating unified command between LCFR and LCSO." The authors developed two active shooter command competency simulations that require LCSO and LCFR to form unified command and manage the initial response. The simulations reinforced accepted response practices, such as identification of cold/warm/hot zones, early unified command, rescue task force team deployment, and protected corridor establishment. The simulations were packaged into a unified command competency training and simulation program. Through the facilitated debriefings with participants and facilitator debriefs, three types of lessons learned were identified: 1) high threat incident response lessons, 2) lessons for conducting AVIs in the command competency lab, and 3) active threat operational considerations for command officers.