I was going to say it beggars belief, but sadly that's not true.
These creatures (they are not animals, animals don't behave in this fashion) are beyond the pale. How can our society have failed so badly as to produce beings so incapable of making such basic decisions about right and wrong?
But it is more than this. The crime is heinous, almost beyond words, and it has thrown a spotlight on a very unpleasant aspect of modern society: the neglected fringes. I am not going to put this forward as some way of justifying what was done, that simply is not possible. I don't care how bad your living conditions are you can still choose not to hurt people. What I am saying is that it has, once again, highlighted the fact that our society has its failures.
Were the actions of these villains the product of their unbringing and lifestyle? Some would say yes, but I would rather point to a society that has let someone develop with such a warped set of values that would allow them to even contemplate such a grievous assault as this. As MA-C said they won't even lose sleep over it because it simply will not impact their conscience or morality. And yet there are others living in similar conditions who would not even begin to think about doing something like this.
I just don't know.
I'd have to say yes, its the upbringing. We, as a society, can only help people so much. If they choose not to correct themselves or turn their life around, we can't control that.
You're right though...going by the reaction of one of the neighbors, and her comment, these people won't give this a second thought. I really hope these people who did this get sent away for a long time.