A “good guy with a gun” is the only thing to effectively counter people intent of committing mass murder. “Gun free zone” signs tell mass killers that the likelihood of their facing an armed citizen to stop their attack is extremely low, and indeed, seems to be something mass shooters look for when selecting locations for an attack.

That message has filtered through to the saner minds of the education establishment in Ohio, and dozens of schools are opening up to the idea of concealed carry on campus.

Dozens of school districts across Ohio made some allowance for handguns on campus in the year following the shootings at Sandy Hook Elementary in Newtown, Connecticut, a recent Buckeye Firearms Foundation (BFF) survey found.

“There are at least 20 different school districts in Ohio that have authorized individuals such as teachers, administrators and parents to carry firearms in schools,” BFF President Jim Irvine wrote on December 11.

“The list includes rural, urban and suburban schools. It includes public, private and parochial schools. It covers small, medium and large schools and all grade levels,” Irvine explained. “In short, it is a cross section of Ohio, and the United States of America.”

“Some of these districts took quick action and had authorized people carrying soon after the Sandy Hook killings,” Irvine wrote. “Others waited until the start of the current school year.”

“Many are considering expanding their program to include more people as they realize there is great upside potential and almost no downside issues with authorizing good people to carry the tools necessary to stop an active killer,” he added.

It is an exercise in common sense, perhaps best shown by a study in contrasts of what could have been very similar events.The shootings at Arapahoe High School and Sandy Hook Elementary were a study in similarities in intent that resulted in dramatically different outcomes because of the presence of an armed defender.

At Sandy Hook, the shooter faced no credible opposition for roughly five minutes until various police units could converge from some distance away. As a result of this delay, he was able to murder 26 people before committing suicide as law enforcement officers closed in.

At Arapahoe, the shooter’s spree was cut short by the presence of an armed deputy sheriff who was in the school as the school resource officer. The shooter was only able to murder one student before being cornered by the deputy in less than 90 seconds, at which point he committed suicide. It is worth noting that the Arapahoe HS shooter had 119 unfired shotgun shells and a list of five target locations within the school. If the deputy had not arrived, he almost certainly would have taken more lives.

Any serious study of mass killers—and just as importantly, would-be mass killers that failed after they started their attacks—shows that an armed response by anyone dramatically shortens the opportunity window for the shooter, and that many, if not most would-be mass shooters commit suicide if they face even the hint of a credible armed threat. The Arapahoe HS shooter committed suicide apparently without even seeing the sheriff’s deputy; he heard the deputy identify himself and committed suicide. The Clackamas Mall shooting was cut short after the shooter simply saw a concealed carrier with a drawn weapon, at which point he ran away and committed suicide. Mass shooters and wannabe mass shooters generally do not want to be shot at and injured, and run the risk of being taken alive.

Some communities have responded to the potential threat of mass shootings by posting armed private security guards or sworn law enforcement officers in schools, but other districts either view the threat to be too small to address or too expensive, and have opted to go the route of allowing faculty and staff to carry concealed weapons on campus.

This is what intelligent, data-driven people might be tempted to call “gun sense.”

Perhaps that is why the anti-gun movement relies almost exclusively on fear instead of logic.