Hey! I have an 11 month old puppy and he is getting very aggressive with some people. Like when family or friends come over he will bark when they first come in , but after they pet him he shuts up. We put up a chain link fence to keep him in the yard, but somehow this morning he got out when the trashman came. He was barking and biting at the mans boot. I called him to come to me and i mean he looked in my direction and started again. i did see the man kick him in the head ,so i think thats why he got so bad. he only does this with certain people. How can I break him from this while he is still young? Any suggestions will help...my female Daisy never did this and she loves everyone. Always gentle and sweet. Mack is the devil himself.lolI dont want anyone to be scared of him and i told the man that he was still a puppy and that he barks, but he insisted that he was trying to bite him. I hope they dont call the police to come out.