A physical fence may have given the police officer enough time to get there, and it may have been enough of a barrier that the dog was ok with the status of the turf. It may have made the difference.
One of our k9s came after Dubya while I was walking him. I heard them shouting at the dog and kept walking keeping Duby with me until I could turn around in front of my dog holding his head toward me. The two officers had the dog on the ground. Scarey. Dubya was an intact male, and that could have been the difference.
Still, how do they let the dog go after a perp if the dog is so dog aggressive that it will attack a dog that might be around?
I think that the sherriff's department made the choice due to a couple of incidents, and if they were to rehome the dog, with all of its training, and something were to happen, they may have been liable down the line.
I think the officer/handler should be off the k9 corp and not given the possibility of a new dog. I think he screwed up big time.