You, and your family seem unable to accept that what your wife did was correct, and dare I say, morally right. How could it be otherwise? It's not right that a child would kill a pet...even if he didn't mean to. The fact that he was violent is questionable and very worrying. And at his age, his parents are responsible for his behaviour. Obviously your family seems to believe that family comes before what's right. So they are ok with Sal and his wife's negligent behaviour...but what your wife did is wrong?
Sounds extremely dysfunctional.
Posts can't be edited...you are stuck with what you've written.