I have no idea how she secured the guns, but even a lock and key isn't too likely to stand in the way of someone obsessed with outdoing the murder score of Andrs Breivik.<quoted text>
Quit splitting hairs. While the psychological conditions of Adam were not perhaps brought about by poor parenting, the outcome was, and perhaps may have been avoided if his mother had kept guns and violent video games out of her house.
What mother attempts to "bond" with her troubled son over a day at the shooting range? And then leaves him unattended without securing the guns by safely locking them up where he couldn't get to them?
The fact still remains, however, that kids who present in the way that this one did at a very early age are typically not well handled at school and this one appears to be no different.
I would suggest that by the time this whole thing wound down the woman had plenty of troubles of her own--very likely in the form of PTSD--from the experience of being the primary (and perhaps sole) caretaker for an adult with very serious mental disturbances. And it would appear as though those disturbance had first appeared many years prior.