Fawn, while I agree it is human failing that brought the cat to it’s death, I do not for a minute blame the officers who had to act.
It's an unpleasant reality, and applies to 'innocent by insanity' defenses as well, but regardless of the 'how', it is society's obligation to put an end to the threat.
The cat was, in fact, innocent; she was simply being a cat.
The cat was innocent; she was not able to choose where she was when the kids showed up, she was not able to rely on protection from others.
The cat was innocent; she relied on instinctive defense measures - attack if you cannot retreat - generally good advice for humans as well.
But ultimately, judging an angry, blooded, tiger to be a threat to additional citizens, and themselves, the cops had no choice. Besides, much like the cat, they also acted on instincts developed in the course of their duties - difference is that we license police to use force - zoo animals don't have that benefit.