Wait. What? As long as your kids live at home even into adulthood the parent should be monitoring all their spending? So they were supposed to be a super controlling homeschool family that didn't allow him to do anything till he moved out and got married.
I can't tell if this is sarcasm or not. But if not, geez, parents just can not win. The truth is this guy was entirely responsible for the horrible things he did. And life sucks. We just can't predict who the next loser will be who decides to kill.
Personally I don't want to live in a world where we just start preemptively locking up loads of people on the off chance they "might" be a bad guy. Or telling the parents of 24 yo's it's their fault they didn't monitor their adult child's spending and determine the parts must be for bomb making.