Dunkin has been socialized with other dogs at the dog park and the two big dogs my in-laws own. However, we have had two incidents where Dunkin appears and acts very mean and aggresive towards other puppies. Almost if he would attack if I let go of the leash. He is so playful towards bigger dogs and kids but any dog that is a puppy he freaks out. It really makes me upset and embarrassed. One time it was in our home and the other time it was out at Petco! I Petco I made a point to be uninterested in the puppies to see if jealously was his issue. He seems mad anyways! I'm nervous that he will turn out to be a mean dog! Whats up with that? Any thoughts?