Aldrich is an example of a new and troubling type of violent American extremist, according to law enforcement officials and political scientists: the grab-bag radical.

Past perpetrators tended to fall into two broad categories.

One includes militants recruited and trained by others to defend a cause, such as the anti-government beliefs of far-right militias. The other was a previous breed of “lone wolf” terrorist, obsessed and informed by a clear issue that motivated attacks, like the bombings by Ted Kaczynski, the “Unabomber,” because of his opposition to technology.

Aldrich, by contrast, embodies a novel extremism forged distinctly by today’s polarized politics, fragmented online discourse and prevalence of fictional narratives. Like other actors behind a wave of political violence analyzed by Reuters, Aldrich wove his own brand of fanaticism from disparate strands of conspiracy theories widely circulating on the internet.