During a family session, it is revealed that an older child has sexually assaulted a younger child. Both children live in the same home with their parents. What is the PMHNP's next step?

Call the police to have the older child arrested.

Maintain a calm demeanor, step out of the room, and call 911.

Sign an order of involuntary consent for the older child and have him sent to an inpatient psychiatric hospital for treatment.

Ensure the older child is not left alone with the younger child and call child protective services.