The Trick of Stealing Money "Legally"

This happened in Houston on 05/19/2016. The man in the video ask me to change him two $10 dollars bills for one $20 dollars bill and then looks what happens....
Later on We found out he went to Nick's bar and did the "Trick" to the bartender with all success and later to La Michoacana and so on....
We call the police and he said that there is nothing they could do to press charges against him due to the "Lack of Prove"