Final answer:
The key purpose of debriefing after an active shooter event simulation is to offer emotional support, identify areas for improvement, and review the actions taken during the exercise.
Step-by-step explanation:
The most important purpose of debriefing following an active shooter event simulation is D) All of the above. The debriefing session serves several critical functions. First, it provides emotional support to participants who may have experienced stress or trauma during the simulation. Secondly, it is an opportunity for identifying areas for improvement in responses and procedures. Finally, reviewing actions taken during the simulation allows participants to reflect on their decisions and behaviors in a controlled, learning-focused environment.