That is sad but it happens all too often. If the pit can't win the fight, it is either killed by the owner, killed by the other dog it is fighting or used as bait to train the other dogs to fight.
There are some really sick and stupid people out there. Pitbulls are great dogs and it is such a shame that the breed is being so abused.
Was the owner reported?? I would have reported him as this cycle will continue unless someone puts a stop to it!!