Odometer Rollback Scam 2010 Honda Odyssey


Hello Scotty, thank you for all the advice so far.
Not so much a question for a mechanic but I thought I'd ask you anyways.
I just went to look at a 2010 Honda Odyssey EX-L today that was advertised to be 100k miles, listed for $8,400. It was basically the KBB value since it was also in very good condition. When I went to see the car, the guy selling the car which I now think was giving me a fake name, told me that his uncle had this car and he wanted to sell it to buy a new Sienna now that interest rates on car loans are really low. I wanted to run a Carfax report on it but I wasn't getting any signal and there were others buyers scheduled to see the car so I made the foolish decision of paying $8,200 cash for the car. I got the title which had the name of the guy's uncle that he on it and drove to my mechanic. I told the mechanic to do a VIN inspection , change the oil, and tell me the condition of the car. Then I went home. When I went home I run the carfax and it turned out that the car had 190k!! miles on it. Which would place its KBB value at around $5,500. I then went to my mechanic and asked him if he could prove that the car had been tampered with but he said that is was practically impossible and left me on my own devices. My mechanic also said that the car was in great condition even with 190k miles and said I got a good deal even for 8k dollars which I don't really understand. I called the guy I bought the car from and he said that the Carfax must be wrong. I told him I want my money back and he can have his car back but he got hostile and told me to stop calling him. So my question is what to do next. I still haven't registered the car to my name but I am planning on doing it tomorrow. Should I go to the police? Call a lawyer? I think I may have his real name and place of business after some digging as well. And even though he has now removed his add, I have several screenshots of it showing that he advertised it as 99k miles.
Any help would be appreciated!!