Alexis chose a weapon, as it happens, that has been endorsed and promoted by the vice president of the United States, who makes it his business to tell us which guns should be banned and which are all-American tools of self-defense. The shotgun is firmly in the latter category. Joe Biden sounded like a pitchman for Remington at a Facebook town hall earlier in the year when he urged a mother concerned about safety: “Buy a shotgun, buy a shotgun.”

This may be fine advice, but there should be no mistake: Shotguns are dangerous. When it comes to “the sport of killing innocent people,” almost any gun will do, especially if it is in a permissive environment where no one else is likely to be armed. This makes a hash of the conceit that the government can ban a few guns — based largely on cosmetic features — and make shooting rampages less likely.

Other common panaceas would have had no effect, either. Alexis bought his shotgun from a duly licensed dealer, not at a gun show. He passed a federal background check with no problem. He didn’t have a high-capacity magazine. He reportedly got the handgun or handguns he may also have used in the attack after shooting a security officer.

So the Navy Yard rampage demonstrates the essential sterility of the gun control debate, and all the ill-informed nattering that the likes of Piers Morgan can muster won’t change that fact.