Up until the 1960s, almost all of the mass casualty events at schools, including the largest one in US history, were accomplished using explosives. If you only

Up until the 1960s, almost all of the mass casualty events at schools, including the largest one in US history, were accomplished using explosives. If you only look at shootings you'll miss the bigger picture. The most interesting question that arises from this is why the switch from explosives to firearms by perpetrators of mass casualty events. It wasn't due to regulations on high-explosives, which were essentially cash-and-carry for the entire 20th century. On the other hand, regulation of firearms greatly increased starting in the 1960s.