When I worked at the vet office, we had contracts with several of the local K9 units and let me tell you, a few of those dogs really scared me. There are very few dogs I've met that I was really scared of but two police dogs in particular did.
There's a retired police german shepherd that came in for a bath and brush one time. I will NEVER do that dog again..he scared me to death. The guy had a muzzle on him when he brought him in, and he's like "well yeah he doesnt really like strangers." The muzzle was waaaay too loose so I had to put another one on. I couldn't even touch that dog withouth him not just growling, but lunging at me. He was completely unpredicitable and vicious.

I know police dogs are trained to attack....but they shouldn't be attacking any stranger near them!

Just fyi I'm not saying that all GSDs are vicious (I love the breed!) nor that all police trained dogs are that way, just that the experience I had with one was unpleasant.

It's unfortunate such a thing like this had to happen....ANY dog should be securly kept in a house/yard, but ESPECIALLY a dog with training like that!