Five years ago, Leo McCarthy lost his 14-year-old daughter, Mariah, when a drunken driver hit her and two of her friends as they walked down a sidewalk near her home.

But he refused to let her tragic death become just another statistic.

Knowing that the driver was 20 years old — not even old enough to drink legally — McCarthy made an unusual promise to the teenagers attending Mariah's memorial service in Butte, Montana.

If they refrained from drinking until the legal age, he'd give them one thousand dollars.

In a state which is notorious for its drunk driving rates, Mr. McCarthy's offer has inspired abstinence in more than 140 high schoolers who have taken "Mariah's Challenge."

(WATCH the video below, or read the CNN Hero story here)