What is the immediate action that must be taken when a shooter opens fire?

When a shooter opens fire, the most immediate action that must be taken is to address the threat by proceeding to confront the suspect. The primary objective in such a high-risk situation is to stop the shooter and prevent further harm to individuals. Timely intervention can be critical, as every second counts in these scenarios where lives are at stake.

Establishing a perimeter, evacuating the building, or contacting the media are important actions but are secondary to the immediate necessity of neutralizing the shooter. Evacuating could put individuals at greater risk if they are exposed while attempting to escape, and establishing a perimeter is essential after the immediate threat is contained. Contacting media sources for updates is not relevant in the critical moments right after a shooting begins, as the focus should be on ensuring safety and stopping the violence. Thus, confronting the shooter is the most urgent priority.