I have a 2yr old pitbull, who 90% of the time is the most docile, sweet creature known to man. He is fixed, has been through basic obeidience, and is using the E-collar. At home he has no issues with his brother, smaller sister, and house cat, but when we are at the parks he becomes a big bully, especially with small dogs. This is unacceptable behavior and I need help breaking it. I am willing to do anything to get this to stop, please help!!!!