Mass shooters, although almost always male, in many other ways grimly echo the diversity of American life. Dylan Roof in Charleston is white. Elliott Rodgers at UC-Santa Barbara was of mixed English-Chinese origins. Major Nidal Malik Hasan of Fort Hood is of Palestinian descent. Aaron Alexis, who killed at the Washington Navy Yard, was black. Their belief systems are distinctive too, sometimes right, sometimes left, sometimes religious, sometimes secular. Some are deeply mentally ill, but many more are not. And so on backward through the list of these distinctively American slaughters.

Despite their differences, however, these mass killers shared one quality with each other and with every other American besides: easy access to deadly weapons.

Gun massacres are regularly followed by another uniquely American ritual: a cacophony of voices exonerating American gun laws for American gun violence. “What type of gun law would have made this situation not occur?” objected South Carolina’s junior senator, Tim Scott, on Fox News. Former Texas Governor Rick Perry dismissed the “knee-jerk reaction” that “if we can just take the guns out of the hands of everyone in this country, these types of things won’t happen again.” Gun advocates boldly insist that gun massacres occur because Americans are not yet heavily armed enough. In the end, the political system shrugs its collective shoulders: The fact that Americans are regularly gunned down in large numbers by lone gunmen—and that Britons, Germans, French, Italians, Canadians, Japanese, Australians, New Zealanders, South Koreans, Danes, Swiss, Poles, and Spaniards are not—is just one of those unfathomable mysteries, like the fate of the crew of the Mary Celeste.