Do you trust the motorist in the car next to you? Based on what, his license and registration? Does that guarantee he's a safe driver?

Then what makes anyone think the legal owner of a firearm is a safe gun user? How many of us ever carefully ponder the distinction between owning a gun and using it, the threshold crossed going from gun owner to gun carrier to gun user? Given frequent arguments that more armed Americans could prevent mass shootings, it's an enormously relevant question.

In last week's disturbance among teens at Arden Fair mall in which people initially thought firearms might have been involved, some online readers of The Bee's coverage said they'd be prepared to use their own concealed weapon to arrest the situation.

"I would have gone toward the gunfire," one reader in Texas wrote, confident that in Texas, "more than likely I would not be the only one."

Confident, too, that anyone moving toward a tense, fluid shooting situation was well trained in firearm use?

"Smart people in an encounter like that would keep their concealed weapon concealed and leave the scene," former Sacramento County Sheriff John McGinness told me.

Nine of my childhood friends currently in law enforcement, from the NYPD to federal agencies, concurred. Do not engage, for any number of reasons.

How many people armed with a handgun can hit their target beyond, say, 20 to 30 yards, assuming they can even get that close under fire?

If you decide to engage, what are you looking for? Someone young and a minority? White, like Adam Lanza, or older, like William Spengler, who ambushed firefighters in upstate New York? Or just a person holding a gun? You're a person holding a gun. Other legally armed citizens, off-duty cops and on-duty police responding to the scene could easily confuse you with the shooter or his accomplice.

Our Texas friend may trust his own skills. Can he trust anyone else's? How can he know? How can any of us?

To prepare for shooting scenarios, law enforcement personnel undergo intense training as a matter of routine. How many gun owners do that?

A concert musician at the height of his career still practices obsessively – four or five hours a day. There's always that guy who can play "Chopsticks," or fumble his way through the Peanuts theme, but Carnegie Hall ain't his destiny. How many gun owners can only play "Chopsticks"? How many think they're concert artists because they hit the range once a month?

On the road, we can reasonably assess the skills of fellow motorists – avoiding them when necessary. We can't know the skills of a responsible gun owner until a violent situation erupts. Even the gun owner can't guarantee how he'll react. And bullets travel way faster than cars. A musician's wrong notes cost no one his life.

So are we really sure about arming more people, or teachers? Or putting armed guards in schools? Against an attacker in body armor with the advantage of surprise and a weapon discharging multiple rounds a second, the first school-shooting victim almost certainly will be the armed guard.

"Especially when you consider this," McGinness warns: "School shootings are extraordinarily rare. It's like the Maytag repairman. I don't care how dedicated you are, you cannot stay focused on something that has so little chance of happening. It becomes a desperate waste of resources."

And if it happens, does being armed help? Columbine had an armed officer. Virginia Tech had its own police force. Fort Hood? A military base.

An investigative report by Mother Jones magazine found, "Not one of 62 mass shootings in the United States over the last 30 years has been stopped (by armed citizens). More broadly, attempts by armed civilians to intervene in shooting rampages are rare – and are successful even more rarely. Two people who tried it in recent years were gravely wounded or killed."

I don't oppose gun ownership and have little confidence in the direction Washington currently seems headed on gun control. But I don't think everyone appreciates that you are not protected if you own a gun; you are protected if you know how to use it. Skillfully.

If we conclude, as happens on a daily basis, "Boy, there's somebody who shouldn't be driving," what makes you think that doesn't apply to gun ownership? And we're far more thorough with car ownership than we are with gun ownership.

That the criminal population believes every other person may be carrying "is a good outcome for the public," said McGinness, but he quotes an attorney friend who's "represented the NRA, an ex-Army Ranger, firearms instructor, a gun guy," who likes to say, "Everybody has an uncle who shouldn't be prohibited from having a firearm, but who absolutely should not have one."

Is there any way to address that?

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