get his license plate number down and report him for road rage. thats really all you can do. but DO NOT get out of your car and confront him. you never know what people have taken (drugs or alcohol) and you dont want to be put in a dangerous situation
Hit the brakes,let him hit you,get a check for your vehicle (if you hit someone from the rear, you are at fault 100% of the time,NO EXCEPTIONS! you must be in control of your vehicle at all times)