06/12/2014 at 06:30 PM EDT  Leo McCarthy's world was shattered with one phone call late on a crisp October night in 2007.  An underage drunk driver had killed his youngest daughter, Mariah, 14, and injured two of her friends, less than half a block from his Butte, Montana home.  McCarthy, 54, would later learn that the driver, a 20-year-old neighbor, had been drinking for hours before climbing into his pickup. He pled guilty to negligent vehicular homicide and served nearly four years in jail.  But the grief-stricken McCarthy, his wife, Janice and daughter Jenna, then 17, wanted more than punishment.  "We wanted to make sense of this for Mariah's generation," says McCarthy. "We couldn't bring her back. But we could keep somebody else from losing a loved one to a drunk driver."  At Mariah's memorial service, McCarthy issued a challenge to all of her school friends: Promise not to drink until the state's legal age of 21 – and not drink and drive ever – and he'd award each of them a $1,000 college scholarship.  Starting with 31 students and raising funds from local businesses and private donors, McCarthy's nonprofit  has since given out $185,000 to 185 Montana high school graduates.  Now adopted by 40 high schools and expanded to Idaho, Wyoming, Iowa, Washington and North Carolina, McCarthy's sobriety pledge also has resulted in a drop in alcohol-possession charges involving minors and DUIs among drivers of all ages in his town.  "Things have changed for the better because of Leo," says Says Butte-Silver Bow Sheriff Ed Lester.  Northey Tretheway, 20, signed the pledge after hearing McCarthy speak at his school. With his scholarship, he now attends Montana Tech in Butte, where he advocates for others not to drink.  "Mariah's Challenge and Leo," he says, "are opening a door for all of us to become the best we can be."  The good he has done hasn't made the loss any easier for McCarthy, an insurance agent.  When he steps outside each morning to get his newspaper, he can see the home of the young man who killed Mariah. She was a fun-loving teen who enjoyed volleyball and bowling, lovingly called her parents "ogres" and complained about chores.  "The hurt is always there, every single day," he says. "But I have forgiven him."
McCarthy, whose 14-year-old daughter was killed by an underage drunk driver, has sent 185 Montana kids to college