It could be argued that, because of his age, he didn't know the difference between right and wrong, or that he didn't realize that he was causing injury...
As I recall, when I was about two years old, I sat on one of our cats. No harm was done, fortunately, but I was taught in a damned hurry that that was inappropriate behaviour; that if I did that again, I'd not only have most likely hurt my friend/pet, but also my ass when I got it kicked into next week! Lesson learned - at two years old. I find it very hard to believe that, in six years of life, this child would not have had the chance to learn a similar lesson.
The boy was later brought to the vet's to see the aftermath of his deed, but seeing the the brutalized dead dog had little effect.
Give me a few minutes alone with him in the playground... perhaps after he's managed to untwist himself from the monkeybars and drag himself home with his lips he'll get the point.
"If we had to lose our dog in order for this kid to get some help -- so be it," she said.
I disagree. What if this had been a two year old child instead of a six month old puppy? So be it? Not on your life. No innocent deserves to be taken out of this world in such a cruel, brutal fashion, no matter what species it is.
It's times like this that make me wish that Justice was an unbiased entity that could be called upon. It's times like this that my safe little fantasy world comes crashing down.