Kendall, Call this number:
1-401-568-2533
Glocester Police Department
162 Chopmist Hill Rd
Chepachet, RI 02814
Tell them the situation, and they will direct you to their internet crime division. Most police departments in the US have an officer or team of officers assigned specifically to internet crimes like this, and if they don't have it there, they will give you the number to their partner PD that does have this service. Get a copy of your Paypal payment to this guy, the original auctions you won, and these auctions showing he is selling them. They will ask you to fax or email your documents with a statement, and they will go knock on his door. I'm not joking, I have done it before, cross border as well. I had an issue with a thief in Canada, called the RCMP main division in his province, they got me to his local division, and they went to his house and mom was home. Let me tell you, that little punk probably couldn't sit for a couple weeks after his dad got home. His parents called me and it got resolved real quick. The PD in the US will do the same, I've done it twice, and they will arrest him if he does not resolve this to your satisfaction. I would put the fear of god into him right now and tell him you are contacting that police department. He will know who they are and he will probably start begging you to not report him.
Let me know if I can help in any way bud!