I've had a situation similar to that happen to me. There used to be a guy around here that installed urethane roofs on buildings, for which he needed a source of power. His power cable was a roughly 100 ft. length of ratty-looking #2 SER with UNINSULATED
alligator clips on the end. I came home from work one day and found this mess connected to the main disco (line side, of course) on the side of my house. He was installing a roof on a building next door to me, and had not even asked permission to tap into my service! After I finished chewing him out, I called the police, then called a friend of mine who worked for the POCO to bring his gloves and disconnect this foolishness. I assessed him a fee for using my service, which he paid on the spot, then he picked up his equipment and went away.
I haven't seen him since. He probably electrocuted himself out of business.