Dana Plato's Son Tyler Lambert Commits Suicide

Tyler Lambert committed suicide on May 6, just days before the anniversary of his mother's death.

The 25-year-old died from a self-inflicted shotgun wound to the head in Kellyville, Oklahoma, almost 11 years after his mom Dana Plato took her own life.

His grandmother, Joni Richardson tells PEOPLE that Lambert was experimenting with drugs and alcohol at the time, which she believes were contributing factors to his death.

"It's a shame that such a talented human being would do this with his life," Richardson said. "He had all the opportunities in the world and we just can't understand it."

Plato was a child actress and star of NBC's sitcom "Diff'rent Strokes." Her career was short lived after the series ended and had a few run-ins with the law. She was arrested in 1991 for robbing a video store in Las Vegas.

While visiting her family in Moore, Oklahama, Plato died from an overdose of prescription medication on May 8, 1999.

Lambert was 14 when his mom died.