My only suggestion is not to go to the dogpark.
If this little guy is causing trouble and attacking other dogs, chances are a bigger dog is going to grab him and shake the crap out of him.
Dogs feed off of other dogs. It can cause other dogs to attack the one being attacked.
So there will be blood shed if this is not under control. It could result in a tragic ending.
Does the dog attack immediately or does the dog see other dogs playing and then attack? What are the triggers to these attacks? Has he caused injury to other dogs? What does the owner do when his dog attacks others?
Can you answer any of these questions? If so, then maybe we can provide more insight on what is happening, why it's happening and from there perhaps provide some tips.