The mind boggles at the horror of Las Vegas, where Stephen Paddock perched himself in the 32nd floor of the Mandalay Bay and sprayed bullets into a crowd of outdoor concertgoers in the worst mass shooting in American history.

If this slaughter of innocents were an act perpetrated by a foreign power, the U.S. military retaliation would begin immediately, and rightly so.

The impulse to act to stop the domestic massacres that have become a heartbreakingly metronomic feature of American life is laudable and understandable. “It’s time,” as Connecticut Sen. Chris Murphy said, giving voice to the sentiment, “for Congress to get off its a— and do something.”

The problem is that the “something,” namely all the usual gun-control proposals, isn’t well-suited to stopping mass shootings. But liberal politicians never let the inapplicability of their proposals stop them. The passion with which they advocate for new gun-control measures is inversely related to their prospective efficacy.

The go-to proposal is universal back-ground checks, although the perpetrators of mass shootings usually haven’t been adjudicated and therefore have passed background checks, as Paddock did in purchasing at least some of his guns.

He had no history of mental illness, and people who knew him didn’t report any bizarre behavior. He had no criminal record, beyond a minor violation years ago. He didn’t even have politics that anyone was aware of. ISIS is claiming responsibility, but the FBI says it hasn’t found any evidence of a connection. His brother seemed sincerely dumbfounded and called Paddock “just a guy.”

No enhanced background-check regime, no matter how vigorous, would have stopped him from purchasing guns.

Hillary Clinton immediately singled out so-called silencers, or suppressors. “The crowd fled at the sound of gunshots,” Clinton tweeted. “Imagine the deaths if the shooter had a silencer, which the NRA wants to make it easier to get.” This conjures an image of the killer shooting down people with a gun impossible to hear, a conception straight out of a James Bond movie.

In a piece on Republican-supported legislation to make suppressors easier to acquire (it currently requires a long approval process and purchase of a $200 tax stamp), The Washington Post notes that one of the devices would lessen the sound of an AR-15 to 132 decibels, or comparable to “a gunshot or a jackhammer.” In other words, a rifle still sounds like a gun even with a suppressor.

If Hillary cares so much about the issue, she might take 10 minutes to learn something about it, but gun-controllers tend to be low-information advocates.

Confusion between semi-automatic weapons, which are common and fire once each time the trigger is pulled, and automatic weapons, which are rare and fire multiple times each time the trigger is pulled, is a persistent feature of the gun debate. Many gun-controllers don’t know the difference and erroneously refer to, say, AR-15 rifles as machine guns or automatic weapons.

This is an area where Congress has already legislated, though. It is illegal to own an automatic weapon made after May 1, 1986. While it’s possible to own a machine gun manufactured before that, it requires jumping through extensive hoops and becoming part of a federal registry. The guns are highly expensive.

Finally, there are always calls to limit magazine sizes, although this wouldn’t have stopped Paddock, either. From his outpost on the 32nd floor, he tragically had all the time he needed to load and reload. It took the SWAT team more than an hour to breach his room.

The images from Las Vegas are sickening. There’s the sound of gunfire truly worthy of a war zone as people scream and run and cower, with nowhere to go. This shouldn’t happen in America; it shouldn’t happen anywhere. But that doesn’t mean that the off-the-shelf obsessions of gun-control advocates would do the slightest thing to stop it.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.