I've had a Jack Russel/Beagle for two years now. He's very good with people but bad with other animals. Recently he was laying next to my room mate (that the dog really likes, and has lived with for three months) when he bit him hard in the neck completely unprovoked. It's really unsettling, the dog has never showed any sort of aggression before this. The only thing I can think of that might have caused this was a week earlier, my room mate tried to take a bone out of his mouth and he growled and snapped, ever since then he has periodically growled at him for no reason (like he'll be sitting on his lap and just start to growl at him), and now the attack. Would a dog really hold a grudge over the bone thing for over a week? And what woud cause him to get aggressive so randomly?