Sometimes the best parents in the world end up with a child who does something unthinkable. Sometimes people are just bad or psychopath,sociopath, whatever. I mean - what is to say that he isn't one of the above? 2% of the population are psychopaths.
Anyway - I guess we will never really know, unless they make a movie out of it.
I really feel for that poor boy who died and his family. I can't think of anything more devastating than losing a child.