Nobody ever paid serious attention to Santino Legan, Patrick Crusius, or Connor Betts before they went on shooting rampages that have made national headlines. Legan killed three people and injured 13 others July 28 at a California food festival before…

Terrorism takes diverse forms and attracts different levels of attention. At the time of writing, the New Zealand city of Christchurch is reeling from an attack on Muslims by what appears to be a white supremacist. The death toll, still…