This is a good, solid Malcolm Gladwell piece. You have an inherently interesting story (someone planning a school shooting who confesses in a rather full and polite manner) that develops in interesting ways, with a crunchy layer of theory scattered in the mix and baked on top. You should read it. But if you're not going to then here are the two main ideas and my thoughts about their implications.
The main idea is that riots (and other kinds of antisocial behaviour) draw in progressively more and more well-behaved people. You start with a person who has a "riot threshold" of zero, i.e. who is prepared to throw a rock through a plate glass window before anyone else, and then if there is someone with a riot threshold of 1 nearby (i.e. someone prepared to be the second person in a riot) and then a third, and so on, eventually you get people rioting who are only prepared to riot if everyone else is rioting. Gladwell's idea is that school shootings are becoming like that: you can be a school shooter nowadays without having to be quite as weird as early school shooters.
The other idea in the piece is that people on the autistic spectrum can find themselves sucked into quite serious criminal behaviour simply by having their particular kind of curiosity triggered in the wrong way. This is a rather more precise and scientific theory, and I daresay there is something to it. You can see how becoming a connoisseur of school shootings can be a bad start for the wrong sort of person.
What I found interesting about both of these ideas as put together by Gladwell is that they describe a rather fragile social order. You - yes, you - are only X angry people away from being drawn into a riot; school shootings are a snowballing riot happening in slow motion in front of us; and if you are a little bit on the autistic spectrum then you could find yourself being drawn into all sorts of depravity out of little more than innocent curiosity.
But that is not how society looks to me. I am inclined to think the riot theory, at least, is not the right model for what is happening. It's an idea developed for explaining a riot - something that obeys the unities of classical drama - but it does not neatly fit into a series of individual deliberative acts committed at infrequent intervals by essentially unconnected persons.
There is a nascent and quite different idea in the piece, namely what I would describe as the meme of Columbine. In short, it seems that Columbine has given school shootings a model to be followed (complete with pre-recorded videos of a certain kind, prescribed clothing and so on) and so has perhaps established a fomulaic cultural genre. Rioters don't do that. Once you add that to idea of there being people who get overly interested, without great discrimination, in exploring well-structured information then you get a different kind of mechanism at play. You do end up with some people starting to plan school shootings who are not fundamentally that weird or bad. But it's not everyone. It's just some of those people who might have got interested in trains or Bach or butterfly-collecting or any other well-structured part of human life.
All of which is to take Gladwell's interesting and startling work and end up with something more small and prosaic. I'm sorry to do that to do. But at least I'm not going to end up shooting you, no matter how many people think it's a good idea.