Make sure all windows and doors are locked (they always are when I’m driving), then I immediately call 911. I let them know my location, approximate number of people, and give them a description of the situation.
I ask the Police, “Is help is on the way?” If they say no, I tell them to send Police and ambulance ASAP.
I also ask them for recommendations on what I should do. I let the Police know that I am in fear for my life, and am afraid that my property will be damaged. If I am carrying, I’ll let them know that too. I will follow the guidance given by the Police.
If I am alone in the car, when I get off the phone with the Police, I will start video recording everything happening all around me. If someone else is in the car, they will get the job or recording. I will concentrate on the threat(s).
Of course, you can have a plan like this, but once things start, and you’re stuck, you improvise on your plan. Things escalate, and quickly. You may not have time to call the Police, may be unable to record anything. At a minimum, dial 911, and hang up. The Police (I believe) are required to check out the area when there’s a hang up.
I will use deadly force if necessary to protect my passengers and myself. I will do my best to not deliver a kill shot to anyone (no head or heart shot). That too may change if someone in the crowd is armed. You have to act/react as the situation develops.