My white GSD, Ghost, has decided recently that he will bark and growl at anyone who get's near me. I held his mouth shut and gave a firm "No!" He whimpered at me then growled at my friend again and his barking started back up. I have had a lot of anxiety and depression lately, and I'm worried it rubbed off on him. Either that, or he's decided to be a bad dog. He even jumped up and put his jaws over my friend's arm. Luckily, he didn't bite down. It was like some warning nip. I don't want him to be aggressive, he used to be such a good dog. Now that he's older he is becoming stubborn and now aggressive.
I have managed to finally get him to stop barking at other dogs though. I still need to get him used to seeing them face to face. A neighbor's pit bull got out and ran over to Ghost with its tail wagging. It right away wanted to sniff him and seemed playful. The owner came running behind his dog to catch it and kept assuring it was friendly. Next thing I knew, Ghost lunged at that dog and bit it's neck and took ir down to the ground. I right away grabbed him off and smacked him and said "NO! BAD BOY!! NOO!". He still didn't seem to get that that is bad bahavior.