This happened to a friend of mine! The old man started throwing rocks and shaking the gate, and once they caught on through neighbors being aware of it, they put cameras up everywhere to catch him. They locked the gate and put up a visual barrier too so he couldn't see where the dog was. He then started covering his face and would throw bricks at the dogs! Then he worked out how to open the gate anyway and then called the council to say the dog was out and threatening him.... Eventually they had to get rid of the dog by giving him away or face either putting it in a steel concrete Cage in the backyard for the rest of its life or putting it down. Also if the dog got out once more they would also have been fined $50,000!!!
Whatever you do, try and catch him in the act and report him to police ASAP, before he turns everything around on you!