Dog parks have their place ,but are not for everyone. The dog needs to be conditioned to playing with other dogs first and foremost. It is not the place to learn socialization. The owner has to be educated in body language. Here are some guidelines .
Risky chasing behaviors almost always include out of control and high arousal chasing that may include one of more of the following: group chase, hard physical contact, pinning, high tail carriage, neck or throat fixation and the chasee hiding, or trying to get away.
Mobbing is a group of individual dogs approaching, harassing, controlling or attacking a single dog. This can be with or without bloodshed.
Targeting is one dog following or pursuing another dog relentlessly, exclusively, obsessively. It’s relentless engagement that may or may not include many of the behaviors displayed in Risky Chasing.
Bullying is a form of aggressive behavior through the use of physical overpowering, hard contact, body slamming, hip-checking, shoulder-checking, relentless engagement, chase or ganging up to affect an individual dog.
Hunting is when a dog moves around the dog park going from dog to dog, looking for something to jab, chase, poke, pounce on, roll. This is not looking for a playmate, but forcing himself on other dogs.
here's a good article Animal Behavior Associates, Inc. Behavior Consulting