Sorry to hear what happened DrDirt. Unfortunately in your situation it seems both those dogs were already in the "zone" for your Westie. Their prey drive was up and wasnt going to stop at anything. Its sad how irresponsible those owners were and could give two shits.
As for everyone else that hates "Pitbulls" without a real cause. I send out an open invitation to anyone that would like to meet my real American Pitbull Terrier and show you what a true responsible owner looks like and also how they are not the "killer" everyone makes them out to be. Dont be suprised when you realize how small of a dog they really are.