I link to this article in Wired because I think it's on to something, but either Koerner buries the lede or he misses his own point to an extent.
I see the act of mass shooting in the USA, sociologically, as having reached the point of being a fully realized public ritual: the shooter, authorities, politicians, media, and the public—we all play our roles almost intuitively, without even having to recognize the degree that formality and performance shape our behavior. I cannot fathom what draws certain violent men to want to play the part of the shooter in these tragedies, but I am certain that these are not people suddenly "snapping" in frustration: these attacks turn out on investigation to have been planned over a substantial period of time. Each one draws inspiration from the ones before.
What ISIS has done here, using social media to promulgate instructions on maximum armaments and a fidelity pledge, is they have adopted and extended this ritual to serve their own terror and propaganda agenda. The "open sourcing" of violence is not innovative. It's not always described this way, but particularly in the middle east we've seen a pattern for years of suicide bombers and other violent actors who simply strike on their own, and then various organizations "take responsibility" after the fact. In the current case, ISIS planners have perceived an existing self-destructive flaw in our culture (the tendency for certain unbalanced individuals to be drawn to the role of mass shooter) and exploited it to be both more deadly, and more plausible for them to claim credit for. They have, essentially, weaponized our own culture of gun violence and turned it against us.
No one—least of all me—likes to acknowledge this, but the demonstration of tactical and strategic ability here reaches genius levels. Plainly, this intelligence is entirely twisted and evil, but I don't see a way to deny its brilliance. My great concern is that since 9/11 I have seen little sign that the leaders deciding our responses to this threat have anything smart enough to match it.