I have mostly exhausted my interest in posting about the complexities of the "mad or bad" topic but in this case, based on minimal evidence, I'd guess "bad."
Psychiatry has little influence over evil. That's for theology. Evil fantasies are things we (and everybody, pretty much) deal with routinely, but actions are another matter. The devil is stronger than we doctors are. Some evil is everywhere, from boardrooms to government to priests and pastors to teachers to cities to campuses. Please do not tell me that this kid had "PTSD," or an "anger management problem." Some people lack a moral compass almost entirely, but that moral compass spectrum spans from none to spotty to obsessionally scrupulous and fearful. We can deal with the latter relatively easily, but not the former.
The truth is that some people are "born to be hanged," and, at the least, removed from the gene pool. We too often piously imagine that happy and good are default settings for humans as if we could get everybody there with a rearranged psyche and a right environment (we term that "psycho-utopian"). It's an evil lie and an evil vision because it denies the existence of evil itself. My life, and history, have taught me that sin has great power. For all we know, violence, deceit, and destruction of good cheer are the default settings, and civilized behavior a special, difficult undertaking. That happens to be what Freud concluded, and he was smarter and a deeper thinker than I am. Not to mention many prophets, and Christ himself.
It is a positive comment on our level of Western civilization that we are surprised by gross acts of evil rather than taking them for granted. Quite remarkable in human history.
Good and evil remain the basics, as they always have done.
Addendum: I realize that my metaphors sounded as if I believed that evil is genetic. What I mean is that some people simply seem destined for trouble.
