Really, if you have a big truck, just slam on the brakes. Sue him for whiplash. Tell the cops you saw an animal in the road. Be ready for the retard if he is stupid enough to come at you.
In all seriousness, it sounds like you did the right thing. Stay in your vehicle. Be ready if he approaches. Don't roll your window down enough for him to attack you. LE will be on your side in virtually all scenerios here as long as you don't do something stupid (like getting out with a gun).
G19 G26 G30 Sig 2340 357 Beretta U22 (kid's) Two Saiga 12 Two Draco 7.62x39 "pistols" Colt 6920 Saiga SGL21-94, M92 Krinkov "pistol," PSA Patrol Carbine Saiga 223 CCDW KY