A secondary explosive device has been spotted. What is the recommended action to take?

Withdrawing at least 50 yards and notifying the Incident Commander is the recommended action because it prioritizes the safety of personnel in the vicinity of the secondary explosive device, which is potentially dangerous. This distance helps to minimize risk, as explosive devices can have a significant blast radius, and moving away ensures that individuals are less likely to be harmed in case of detonation. Alerting the Incident Commander allows for a coordinated and informed response to the situation, ensuring that trained professionals can assess the threat level and decide on the next steps.

The other options, while they involve aspects of safety and communication, do not provide the same level of immediate safety for personnel. Securing the area and waiting for further instructions may not be sufficient in a live threat situation, as it does not clear personnel from the danger zone. Attempting to disarm the device is highly risky and typically should only be performed by trained explosives experts under controlled conditions. Evacuating all personnel immediately could be necessary in certain circumstances, but it may not be as effective a response as the recommended withdrawal and notification procedure since it could lead to confusion and increased risk in a chaotic situation.