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When I received the money in my BTC wallet, I assumed that he was the one who made the deposit.
It could be him as it could be any one else.
When someone sends you money (coins) ask him for the transaction ID.
If the transaction has been confirmed (which is not the case here), to be sure the one you are talking to is the one who sent you the coins, he needs to sign a message from the sending address (this is a bit of topic, so I'll leave it here).