hello, I have a 4 year old dalmatian mix. He has always been very active but non aggressive, very affectionate to everyone. We recently moved and since then he has been under stress, scratching and bitting himself. I managed to get that under control, but recently he has developed signs of aggression. He barks growls and confronts new people who come to the house. Today, the house engineer came home, he is someone that comes a lot so the dog knows him but is not very affectionate to him, he barks and growls at him. But today the engineer got bitten by my dog. I am very concerned about this sudden behavior and I do not know what to do. He is my first dog and my parents are going crazy... Any suggestions?