My two AB's are perfect little 7 month old puppies when they go to the dog park and play in the back yard. When we go on walks and pass people they go bonkers, bark and pulling, its when ever their on the leash. At the dog park yestarday when we were ready to leave, Bam Bam had been playing with this dog for almost an hour. When the leash went on he became all aggresive and hostile to anything that came near us, including the dogs he knows. When he's on a leash he thinks everything is a threat and won't play nice with any other dogs. Off the leash he is fine. Has anyone ever seen anything like this before? Suggestions? :? :?