Mass shootings prompt simple explanations of the gunman's motivation. At Columbine High School in Colorado, the killers supposedly snapped after being bullied. The guy who shot up a movie theater in Aurora, Colorado was wild-eyed nuts. After a massacre at a Walmart in El Paso, an anti-immigrant manifesto posted online pointed to right-wing politics. Simple mental illness — if there is such a thing — appears to be the culprit in Dayton, Ohio. Also misogyny. But the Dayton shooter's Twitter feed indicates the shooter liked Bernie Sanders and Elizabeth Warren. So right-wing media blames his progressive leanings.

And when there is no obvious explanation as in Las Vegas in 2017, when the mass murderer doesn't leave a final message and doesn't appear to have subscribed to extremist politics and was financially secure, but drank a lot and may have bought into internet conspiracy theories, we shrug our shoulders and forget about it. But deep inside we believe there is a simple answer. We just haven't discovered it yet.

Gun control advocates want to ban assault rifles like the semi-automatic AR-15 used in so many mass shootings. But even if those guns disappeared overnight, gun-related massacres would still occur, albeit with lower body counts. Which would be nice, but it wouldn't address the big question, the one we secretly ask ourselves after such incidents: where does the rage come from?