Can I just add that it doesn't appear, as you say, that there is any ideological motivation in what happened. It certainly produced a terror response, but unlike, for example, what we were describing with relation to Islamists, it wasn't ideological driven. That's the first point that I would actually make as a distinction.
The other one that really struck me, though, was how a 17-year-old got an AK-47 with all of this ammunition, and people knew about it. Thank God I live in Canada.