Auto Insurance Claims: Scrape with expensive car on freeway--now what?, highway patrol car, pavement markings

Question
Today I was in an accident on the freeway in Wisconsin.  I was two cars behind an unmarked highway patrol car.  The freeway reduced to one lane for construction.  Eight miles of signs, flashing arrows in the last mile, pavement markings, all of that.  It's the police car, a Toyota, and myself in the left lane as the right lane ended.  At the last second before the right lane ended, a newer Mustang suddenly appeared out of nowhere and merged into the right side of my car.  I honked and tried to evade, but he made contact with his left front into my rear right side.  Somehow we both stayed on the road.  Because there was no way to exit in the construction zone, we drove on for a couple of miles to the next exit ramp and then both stopped.  He said "you're going to pay for my car, why'd you hit me, you must have seen me." to which I replied, "I think we will disagree on the causality of this accident, and how could I have hit you with my rear fender just driving in a straight line anyway."  No police report was filed.  I believe that my damage is moderate but his may be expensive given the Mustang (nice one).

My questions, as this is my first accident (I'm 40 with a great driving record):
should I be worried that he will claim high property damages against me?  
Is there a chance I would be found to be at fault?  
Should I file for my own damage with my own insurance company (I already called them and said it was his fault)?  
Any defensive actions I should take now?

Thank you, I have read many of your answers and appreciate your help.  Oh, we are both Minnesota drivers with insurance.

Answer
Hi Roger,

From your description of the events, it sounds like the other guy is at fault. He will likely have a different version.

You should make a claim to his insurance company as he will surely make a claim to yours. The likely outcome though, considering that there is no police report and no witnesses is that each company will do their investigation and conclude that each of you is 50% at fault.  You should resist this as long as you can. You should direct their attention to the point of impact and the fact that that he obviously merged into you.  If the other insurance company does not accept liability, of course you will then have to go through your own.

I hope this helps
Richard Hixenbaugh