That is not necessarily the case (that he is a scammer). Paypal is known to sometimes reverse transactions out of their own initiative, without any intervention of the sender, just because Paypal doesn't like something about the transaction. I know it for sure, as Paypal once to my surprise reversed my payment to someone, without my will. Without any real reason, maybe just because I used TOR to connect to Paypal for that transaction, as I use TOR often even without specific need if it works reasonably fast.