Final answer:
The first step that the incoming incident commander should take is to gather information and assess the situation.
Step-by-step explanation:
The first step that the incoming incident commander should take when assuming the role is to gather information and assess the situation. This includes understanding the nature and scope of the incident, evaluating the resources available, and determining the immediate priorities. By gathering information and assessing the situation, the incident commander can make informed decisions and develop an effective incident action plan.