In one world, a lot of people are blaming themselves over this terrible tragedy, and remembering in cruel hindsight how they could have stopped it -- if only. Parents realize they could have locked the safe (or had one), police can trace back to instances of evolving behaviour problems, school representatives can see the holes in the doctrine of care and monitoring they've been working under and how it's not effective. The province.. . I dunno; allows too many rapid-fire deadly weapons in one place?
Anyway, we're not in that world, because they've been able to project their own guilt at a vendor.