The county sheriff in Logan Ohio thinks that if gun dealer John Downs hadn’t turned away a certain suspicious customer last week we’d be talking about a mass shooting in Ohio.

What Downs did was refuse to sell a 9mm rifle to 25-year-old James Howard, even though Howard’s background check came up clean.

Related: Gun shop owners should know when to cut off would-be killers

During the background check, Howard checked the box that says he had not had mental health issues. That would allow Downs to sell him the rifle. But he told CBS that something didn’t look right.

“The look in his eye, you really can’t explain it. He was going to do something.”

So he sent the guy away.

“And I just said, ‘you know what, bud, I have a really bad feeling about this I can’t sell you the gun.'”

What John didn’t know at the time was that Howard did have a history of mental illness and that earlier that morning he’d tried to attack his former coach at a nearby university, and then had stormed off to buy a gun.

In fact, Howard returned to the gun shop an hour later, but this time, Downs locked the door and took his customers into a back room and called 911. Howard was finally arrested at a nearby Walmart just as he was trying to buy 50 rounds of ammo.

So there it is, a case where the background check failed completely. And what worked was having a gun shop owner who makes it a practice to know who his customers are.

We can’t get too warm and fuzzy about this, though. As it turns out the ammo the suspect was buying was for a gun he had successfully purchased somewhere else.