Semiautomatic guns, and large capacity magazines, have been around for decades and decades, guns were substantially easier to obtain in the 1950s and earlier (mail order, anyone), and gun ownership overall has been falling for decades, but school shootings only started to become a "thing" in the 1980s. So what changed? The lethality and availability of guns didn't change (except, perhaps to become less readily available), so it must have been something else that changed. What was that, exactly?
