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On Thursday, a 16-year-old armed with a pump-action 12-gauge shotgun that his mother allegedly bought him for his birthday and a backpack full of ammunition opened fire at Silver Rail Elementary School, in Bend, Oregon, killing three children and a teacher. A 7-year-old student and another teacher were critically injured. The tragedy could have been worse if not for the heroic actions of an unarmed teacher who threw her cellphone at the gunman before tackling him, and a father of two students at the school, who heard the commotion and used his pistol to kill the shooter.

While both people who intervened to stop the shooter deserve high praise for their selfless heroism, some commentators—including President Donald Trump and the National Rifle Association—are celebrating the “good guy with a gun” while ignoring the unarmed teacher who intervened first.

This “good guy with a gun” myth is a seductive marketing tool for the gun industry. Many find comfort in the promise that the solution to our most urgent insecurities is readily available at the nearest gun shop. If we are afraid, we need only purchase a firearm to ensure we are ready when a “bad guy” breaches our cherished boundaries.

But there are critical problems with the armed “good guy” trope. One is that the most reliable empirical research on defensive gun use demonstrates that incidents in which a “good guy with a gun” stops a “bad guy” are vanishingly rare. The overwhelming majority of fact-based, peer-reviewed research shows definitively that more guns are........

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