Ditto kisses from me, jorgelito.
A pack attack in a dog park is something I have never heard of and wonder if some special circumstances were in place.
The great thing about dog parks imo is that it allows the dogs to associate with each other without the "territory" demand that they feel is required at home. Most dogs truly do enjoy that environment, but pet owners still need to be watchful for problem behavior of some owners. Frankly, the owners of aggressive dogs rarely bring them to dog parks, but there is always the idiot owner that doesn't have a clue.