By Steve Ginsburg

(Reuters) - Pittsburgh Steelers cornerback William Gay remembers arriving at the hospital as a confused 7-year-old trying to understand why members of his family were sobbing uncontrollably.

He soon learned that his mother had been shot in the back three times. The assailant, Gay's stepfather, shot himself in the head, the .38 caliber revolver landing between the bodies.

Gay's mother, Carolyn Hall, was alive for five hours at the hospital before succumbing, while her husband died instantly. If life in a Tallahassee, Florida, housing project was tough already, things just got a lot more demanding for William Gay.

But the 1992 tragedy ultimately turned Gay into an advocate for women threatened by domestic violence, a scourge that landed on the doorstep of the National Football League this year and undermined its leadership.

Several of the league's top players, including Adrian Peterson and Ray Rice, have seen their domestic violence cases play out publicly and sponsors have been vocal critics of the league's initial light sanctions for the stars.

As the NFL tries to re-establish its credibility on the issue, including beleaguered Commissioner Roger Goodell, the 29-year-old Gay finds himself in a unique position of helping fellow players avoid violence against wives, partners and children.

Gay never knew there were problems in his home. There was no fighting and no visible bruises on his mother.

"I dealt with a lot of anger because I felt like, 'Why me?'" he said softly. "I threw out that question a lot. I got to a point where I didn't care. I felt like no one cared about me. Didn't care about school. I started lashing out at people."

WORK AT WOMEN'S SHELTER

Gay was headed down the wrong path until at the age of 12, he received some tough love from his uncle, Army veteran Ronald Hall.

"He basically talked to me like a grown man," said Gay.

"I sat him down and said, 'William you cannot blame the world for what is happening. In order for you to be a better person, you better let it go. You're going to end up in jail or dead,'" said Hall. "He took it to heart."

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Gay received a scholarship to the University of Louisville before entering the pros as a fifth-round draft choice for the Steelers in 2007. Soon enough, he had a Super Bowl ring when the Steelers won the championship in 2008.

For years, he has quietly worked at the Women's Center and Shelter of Greater Pittsburgh where his key role is speaking to the mothers about domestic abuse.

"To hear it from someone who was a child whose mother was murdered really resonates," said shelter chief executive Shirl Regan. "Those talks are done off-camera. Nobody sees that. That's on his time. He does that because it comes from his heart."

While many NFL players wear pink cleats for breast cancer awareness, Gay faced a possible NFL fine for donning purple shoes in October in honor of Domestic Violence Awareness Month.

Beneath the uniform is another reminder of what happened on March 14, 1992, a tattoo seared on to his arm.

"Even though she wasn't here, my mom molded me into the man I am today," said Gay. "I still pray to her all the time."

(Reporting by Steve Ginsburg in Washington; Editing by Mary Milliken and Eric Beech)