I think the rioters were intent on smashing the BMW a representation of wealth, they weren't interested in killing someone -don't do anything to change their mood.
Since you are in Switzerland and have to assume that some of those rioters may also been armed Swiss nationals, pulling a gun in that situation may not be the best move. Driving over them may not be that ideal as well, since the gearing of a BMW is not optimal for low-end work like a truck.
If possible, perhaps he should have used the car to slowly push the rioters aside until enough clearance happened to get away -all the while letting them beat-up the outside of the car. Better to trade the car for your life.