Possible Buyer Scam

Description

I have a buyer I’m suspicious of. 1 guy answered my ad for a product and said he would buy it but I had to talk to his friend. So I called him and he asked me a couple questions about me (not the product), started calling me ‘buddy’, etc. Then he paid me twice. He emailed (and called me, left a voicemail) me to inform me that, so I refunded the first amount. Now I feel I’m going to get scammed somehow and don’t want to do business with him. I can refund him for the original amount, I’ve read that I could still be scammed. What should I do?