Those who have never tried to talk somebody out of committing mass murder can’t know how well, or poorly, they would handle such a crisis.

But this much is certain:

Nobody could have done a better job of defusing a ticking human time bomb than Antoinette Tuff did Tuesday at an elementary school in Decatur, Ga., slightly east of Atlanta.

A 20-year-old man with a history of mental illness entered Ronald E. McNair Discovery Learning Academy, named for the Lake City astronaut killed aboard the Space Shuttle Challenger in 1986. The intruder, Michael Brandon Hill, carried an AK-47 high-powered rifle, hundreds of rounds of ammunition and seemingly horrendous intent.

According to law enforcement officials, Mr. Hill fired at least six shots in the front office of the school. Fortunately, nobody was hit by those rounds — nor by the shots the police fired in response.

It took more than good luck, though, to avert a tragic outcome at a school with more than 800 students. It took stunning grace under pressure by the aptly named Ms. Tuff, whose successful attempt to talk Mr. Hill into surrendering was captured on her 911 call. For more than 20 minutes, Ms. Tuff, a school bookkeeper, stayed on the line — and somehow stayed outwardly calm.

On the tape of that call, released Wednesday, Ms. Tuff told the dispatcher that Mr. Hill said he was “not on his medication” and that he “had nothing to live for.”

Yet her message of empathy eventually brought out the armed intruder’s better instincts. On the 911 call, he can be heard in the background, expressing his erratic, dangerous state of mind.

However, Ms. Tuff can be heard, too, repeatedly offering him soothing — and ultimately persuasive — advice. She told him: “We all go through something in life. My husband just left me after 33 years. I got a son that’s multiple disabled. .... But look at me now. Everything is OK.”

Mr. Hill finally gave up. Then, after the police took control of him, Ms. Tuff finally released her pent-up dread to the dispatcher: “I’m going to tell you something, baby: I’ve never been so scared in all the days in my life. Oh, Jesus! Oh, God!”

Mr. Tuff later tried to defer the praise she had earned to a higher power: “I give it all to God, I’m not the hero. I was terrified.”

But if Ms. Tuff isn’t a hero, there’s no such thing.

The folks at McNair Academy know that. So when those children returned to that school Thursday, many of them brought flowers and other gifts to Ms. Tuff in rightful gratitude for her life-saving courage.

And that dispatcher got it right with these words to Ms. Tuff at the end of that 911 call:

“You did great.”