Traveling on Shabbat in a place of safety

Hello Rabbi,
Let’s say someone is transporting a critically ill patient to the hospital on Shabbat. After dropping off the patient, how should the trip be ended? I saw it written online:
At the end of the trip, since there is a concern about danger in leaving the engine running or the keys in the ignition switch, as someone could enter the vehicle and cause an accident, it is permissible to turn off the engine and remove the keys from the ignition switch. He should do this by changing it, such as between his two fingers.
The problem is that as far as I know, there is no real concern about leaving the engine running, or leaving the key in the ignition when the car is off. What’s more, if you turn off the car, there is still a problem with shaking the car key, since it is locked. I thought that maybe there is a place to allow it so that people don’t avoid driving patients to the hospital for fear that the car will be in danger after the trip. How do you think it is right to drive here?
Best regards,