What happens next? Who is to pay?

I was stopped completely at a red light, one car in front of me and one car beside me. A F-350 diesel) (possibly a farm vehicle) did not stop and hit me from behind. He hit me with so much force, that even though I was wearing my seat belt, it twisted my body and the right side of my head still steering wheel, then came back and hit the head rest. It also pushed my car into the car in front of me. That car wasn't damaged, just scratched along the bumper. I although was. I was dizzy and was having head pains. I finally managed to get out of my car, and the guy behind me was out of his vehicle, and I was upset and I yelled "are you drunk?" and he replied "yes". I told the officers this when they arrived but don't know if they documented it or not. They took me VIA ambulance to the ER for test, and released me. with concussion and back sprain. I was hurting very bad the following day and went my GP and she diagnosed me with Whiplash. Do I need an attorney? or wait on Insurance?