17-year-old high school lacrosse player Grant Mays in Cincinnati got hit in the chest with a ball earlier this month and his heart stopped.

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It caused something called commotio cordis, where your heart gets caught between beats, and can't start up again. There have only been 180 documented cases in the past 20 years, most of the time it's deadly.

The athletic trainer for the other team was a guy named Craig Lindsey. As soon as he saw Grant fall down, he ran out on the field, saw a red mark on his chest and knew what happened.

Lindsey used a defibrillator to shock his heart back into rhythm, and it saved the player's life. Grant was back in school a few days later, and also graduated over the weekend.

Here's the best part. Even though he never had to use it before, Craig says he's had his defibrillator at every sporting event he's covered for the past 21 years. It finally paid off.

Read more at FOX19.