Refuse to pay deposit back

This guy Alex is a shark. I order a trailer to operate with 24v lights and paid the deposit and send proof from my bank the previous day, on arrival the next day he says they don't have. I ask for my money back; he says he don't have it and threaten to assult me should i not leave his premisses. I also wrote an email claiming the money back, he reply in very in very bad language telling me to F**k**f