The comments were numerous, here is one from Malcolm Gladwell:
I see that someone included a link to my recent piece in the New Yorker on this very topic–trying to understand the rash of school shootings. In that piece, I used Mark Granovetter’s theory of riots. Granovetter’s original article is well worth reading: http://vserver1.cscs.lsa.umich.edu/~spage/ONLINECOURSE/R2Granovetter.pdf
Gladwell’s original piece is here. And here is a comment from Peter Turchin:
My explanation of why the rate of indiscriminate mass murder increased 18-fold between 1960 and 2010 is developed in a series of blog posts. The first one is here:
and links to the rest are at the end of the first post.
See also Steve Sailer’s varied comments on the evolution of serial killers, and related matters. There are other interesting comments as well.