William Saletan examines the case of the "armed hero" who rushed to help when he heard the Giffords shooting—and almost shot an innocent man in the process.

Now comes the tragedy in Tucson. And what do gun advocates propose? More guns... The new poster boy for this agenda is Joe Zamudio, a hero in the Tucson incident. Zamudio was in a nearby drug store when the shooting began, and he was armed. He ran to the scene and helped subdue the killer. Television interviewers are celebrating his courage, and pro-gun blogs are touting his equipment. "Bystander Says Carrying Gun Prompted Him to Help," says the headline in the Wall Street Journal.

But before we embrace Zamudio's brave intervention as proof of the value of being armed, let's hear the whole story. "I came out of that store, I clicked the safety off, and I was ready," he explained on Fox and Friends. "I had my hand on my gun. I had it in my jacket pocket here. And I came around the corner like this." Zamudio demonstrated how his shooting hand was wrapped around the weapon, poised to draw and fire. As he rounded the corner, he saw a man holding a gun. "And that's who I at first thought was the shooter," Zamudio recalled. "I told him to 'Drop it, drop it!' "

But the man with the gun wasn't the shooter. He had wrested the gun away from the shooter. "Had you shot that guy, it would have been a big, fat mess," the interviewer pointed out.

Zamudio agreed.

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