Holy fuck. And I see from the article the dog had been with the program for five years. While they noted how long the officer has been with the department (23 years), I wish they'd also noted how long he's been a handler, and how long he'd been a handler for this dog.
I reflexively blame a handler for dog problems, that's the answer 99% of the time - and just as I typically hold adults accountable for how their kids behave. But, hell, dogs can wig out - same as people. But this is about as rare as it can be without NEVER happening.
Oh, a meaningless side whine - made me nuts that the reporter referred to the animal as "A K9 dog" or "A canine dog," which of course is like referring to a "feline cat." And when I hear cops say, "I work the K9 dog car..." it sets my teeth on age, no different than when I hear "supposebly" or "irregardless."
There are cases where genetics are involved with vicious behavior. Not everyone is Cesar Millan, not everyone knows how to handle a dog who has a tendency to go into a fit of rage. It doesn't mean the handler was abusive, although he could have been we don't know. I remember them putting down puppies at the humane society who showed aggressive behaviors and one rule of thumb was any puppy who went for the face to bite was a risk. A dog who continues to bite, especially in the face area, well that's a tough case to break.
I actually am not against putting a dog down if they display certain aggressive tendencies that are beyond my ability to control, but it's a last resort. Almost always it's the handler's fault, or the fault of an unknown past, but there are, like humans, always exceptions to that rule.
The bit with the mop almost had me fall out of my chair!! 
