What should the first arriving Company Officer do upon reaching the scene?

Upon reaching the scene, the first arriving Company Officer should assume Command. This action is crucial as it establishes leadership and ensures that an organized response can be coordinated among the arriving units. By assuming Command, the officer takes responsibility for the situation, enabling them to assess the scene, make tactical decisions, and communicate effectively with other personnel.

Assuming Command allows the officer to direct resources, implement strategic plans, and prioritize actions based on the current circumstances. It sets a clear chain of command which is essential for maintaining order and safety during emergency operations.

Each of the other options, while important in different contexts, would not be appropriate for the first action of the arriving Company Officer. For instance, initiating a Level II stage typically happens when the incident is anticipated to require additional resources, but this would come after assessing the scene and establishing Command. Preparing for evacuation is a critical step in specific scenarios but would follow the initial assessment and Command establishment. Beginning an investigation may be necessary but is generally not the immediate priority upon arrival; instead, it's part of the overall incident management once Command is established.