Utoya... Christchurch... El Paso... that shrieking sound is the strings tightening, to snapping point. Three major white supremacist massacres, with a number of "smaller" ones, attacks on churches and synagogues, interspersed. As violent Islamic extremism has been contained and demobilised in the West -- although it may be a pause, rather than a cease -- hard-right white terrorism has become patterned and regularised.
Anders Breivik and the killers that have followed him have, at some point, made the decision to be lethal, but have deliberately distanced themselves from groups they've been involved in, in order to be more effective. Thus they look like loners, and can be written off as such, when they are in fact one-man cells: the ultra-violent wing of the broader political right, owned by it, and in dialogue with it.