Going with the idea the boy did commit these crimes, my issue is how easy it is to dismiss the boy as a spoiled monster that in a tiff decided to murder his father and his friend. One thing for sure, if true, the child did not spoil himself. If the father had spent all his time and energy with this boy and then when his life changed he didn't take the time to help his son adjust to these huge differences in both their lives, he should have. If the child was acting bratty, and this formerly doting father decided to hit around on the boy, and, worse yet, let other people do it for him, to convey he was not center stage anymore, I can see an immature, unbalanced child becoming defiant, feeling abandoned, frustrated, and reactionary. Obviously, no one knew how desperate or disturbed this child had become. That close relationship was not as close as they thought. Cherry picking a comment I heard, the grandparents lamented "they" had been too hard on him. Something was amiss whether they dealt with it or not.
Truthfully, I hope this boy was not having to process raw meat in his underwear for the family to eat.
Why would the family throw this underwear away. Where they trying to protect the father or the child? Kind of hard to believe they didn't know it mattered.