Miles is a people loving and sweet dog. I credit this a lot to our docile golden retriever Sadie for showing him the way. I was at the dog park yesterday with the dogs and someone brought a stuffed animal for their dog to play with. At one point the dog dropped his toy and Miles picked it up. Miles dropped it and the other dog approached to retrieve it. I told Miles to "leave it" but in an instant he bared his teeth and went after the other dog. I was mortified. We don't have this problem at home because our other dog is more than happy to share but it appears to be a problem with dogs he doesn't know. Help! I leashed him up after the incident and took him away but I don't think it is the last time and he acted very timid and shy towards humans afterwards.