Older aggressive mixed breed
I have a mixed breed dog who is 13.5 years old. As a stray puppy he was brought home by my teenage girls when only 4 weeks old. We had another dog for many years but that dog died approx 2 years ago. We have now just downsized into a townhome from a house with a yard that had an electric fence. I have just started walking the dog several times a day. He does fine when we are alone, but if he just sees another dog he goes nuts. Also, he occasionally becomes aggressive toward men who happen to walk by. What should I do?