Final answer:
The primary goal when responding to an active shooter or homicide in progress is to minimize casualties, prioritizing the immediate safety and preservation of life.
Step-by-step explanation:
The number one goal when responding to an active shooter or homicide in progress is to minimize casualties. This is the top priority for law enforcement and first responders, as the immediate safety and preservation of life are paramount. Ensuring the safety of individuals in the vicinity takes precedence over the immediate apprehension of the suspect, securing the perimeter, or calling for backup, though these are also crucial steps once the primary goal is being addressed.