Stay inside, keep cool, and lay on the horn, until they do something to prove they intend to breach the car and get to you. Smashing a window, rocking the car, bashing in the doors or roof, whatever. Let them make it look good.
Then floor it.
And record it, most importantly.
Remember this story? During the Ferguson riots, a pack of teens surrounded this Bosnian man’s car. He got out to confront them, and they killed him.