Sorry if this has already been discussed -- haven't quite caught up in the thread -- but I am wondering, when he says "the thoughts won't stop. help me"
1) are we to interpret that to mean he is hearing voices telling him to kill other children and is genuinely reaching out for help?
or...
2) did he deliberately draw that picture with that text anticipating he would shoot up the school, feigning "hearing voices," and setting the stage for an orchestrated insanity defense?
Since the parents obviously have neglected their son's mental health, I'm guessing he wasn't ever seen by a psychiatrist.