well the police will probably tell you to drive off, obviously you can't sit there.. thats not a option you have to do something..
if he's right on top of your car you may never get out before being cracked in the head and yes a crack to the head with a baseball back can very well kill you.
i'd take down his license plat number before i drove off, but i'd stay close enough that i'd see the general direction he went in.
i'd probably even follow him till the cops caught up..
i really dont know how it would go down or what i would do..
i suppose if he went for the windshield im gonna respond with bullets.
maybe with or without a warning.
i sure as hell would'nt get out to talk to the guy, thats for sure.