Someone accidentally sent me money through paypal

[amphoto]

Someone accidentally paid me $15 through paypal, emailed my personal email asking for the money back. I ignored it thinking it was a scam. I saw that there was indeed a payment made to my account of $15. I did some research and saw some similar scams happening so I continued to ignore it. I am now receiving requests for payment from 2 other people asking for payment for their friend. I have no idea if this is scam and I am worried about what might happen.  

[kernowlass]

@amphoto 

Sorry but if its not your money and they sent it to your email address accidentally then why would you not refund?

If they sent it using friends/family then you can refund full amount.

If they sent using goods/services then refund minus the fee you were charged and tell them that they foot the fee as it was their mistake.