I picked up a wallet from the ground and emptied it into my pocket
Did you at least try to find the owner of the wallet?
I found the owner but didn't give back the money.
It's not appropriate to take money from a wallet that you found when you know who the wallet belongs to. You should have returned the wallet with all the money still inside, because that's the honest thing to do.
I'm going to keep the money.
It's illegal to steal money like that, you should give this person his money back. It was his to begin with after all.