Read the following passage and answer the question below. 'General Order 34.5 stipulates that an officer involved in a traffic collision with a department vehicle must immediately notify their direct supervisor. The supervisor is then responsible for responding to the scene, conducting a preliminary investigation, and ensuring all required reports are completed before the end of the shift. If the collision involves a serious injury or fatality, the supervisor must also contact the on-call Traffic Division investigator and the Watch Commander. The preliminary report must detail the road conditions, witness statements, and include a hand-drawn diagram of the scene. Failure to complete these steps can result in disciplinary action.' According to General Order 34.5, which of the following is the immediate first step an officer must take after being involved in a traffic collision in a department vehicle?