On Christchurch...

The Internet is a unique tool for self-segregation, you can literally imprison your own mind in grim grievance or dangerous utopian.  In fact thanks to the largely fictitious feeling of anonymity conferred by the internet, self segregation seems built into the process especially for those with strong resentments and grievances. The self segregated are furthermore vulnerable to suggestion, something that can literally be transmitted digitally. Mind you I cannot quantify that statement, but my gut tells me it is so.
So, the suggestible are self segregating themselves in an environment that magnifies dissatisfaction and strongly amplifies impatience and under certain circumstances, moved to homicidal violence.
For the most part, it is solo actors that are moved to shoot up Synagogues, Mosques and Churches, these are famously "soft targets" that offer the homicidally programmed actor the best opportunity to maximize terror without immediately running afoul of retaliation or escalation.
I could dismiss this as a sort of "digital cowardice", but for the moment I wish to dwell on the gruesome calculus that goes into finding a suitable soft target for a shooter who wishes to "Act Out".
Note the singular, shooter.
Thats my rough theory here, "digitally triggered" terrorists at least the wing nut variety, tend to be one-off actors, they rarely seem to have more than one possibly two accomplices, and those circumstances are exceedingly rare, the Tsarnaev Brothers being the notable exceptions.
So if these are solo-single  event perpetrators, predicting their behavior becomes...difficult since one and all, they enjoy the tactical advantage of surprise. Nonetheless, the model does suggest this is still critically a law enforcement model with respect to domestic rightwing terrorism.  This therefore is still a situation that favors rigorous enforcement of existing firearms laws, better definitions of soft targets and above all, better communication between federal, state and local law enforcement. Because at least we now know, what they are looking for...