What should be the security officer's immediate action upon witnessing a hazardous incident?

In response to witnessing a hazardous incident, the immediate priority is to ensure the safety of individuals involved and to mitigate any potential harm. Calling 911 first is crucial because it activates emergency services, which are essential for responding to the situation effectively. Emergency responders can provide medical assistance, control the scene, and deal with any hazardous materials if necessary.

While securing the scene and documenting the incident are important steps to take after ensuring that emergency services are involved, these actions should not take precedence over alerting emergency personnel. Contacting internal security can also be a relevant action, but it often relies on the emergency services being notified first. Therefore, prioritizing a call to 911 reflects a clear understanding of the immediate needs during a hazardous situation and embodies the principle of ensuring safety first.