I found $100 left in ATM

[Sponger.]

Title pretty much says it all. Went to an ATM tonight which was in a mall in front of a few food places. I walk up and hear beeping, then see $100 sticking out of the ATM like someone took their card and just left the money sitting there. I look around and don't see anyone, nobody eating sees what is going on so I set the money on top of the ATM, withdraw my money, look around some more and decide to walk off with the cash.

Should I call Wells Fargo? What should I do with the money? What should I have done differently? etc