On March 26, Clay, who starred on MTV's Newport Harbor: The Real Orange County in 2007, died in the hospital as a result of a self-inflicted gunshot wound to the head a day prior, Frank tells PEOPLE: "It was suicide."
But following his death three weeks ago, Clay's father tells PEOPLE that his son has "already saved about four or five lives."
"Clay had requested that his organs - and he did this years ago when he applied for a driver's license - that his organs be donated to people," says Frank, who adds that his son has "done some amazing things. He's saved about four or five lives already and there should be more."
According to Frank, he was unaware that his son was struggling with anything in his personal life. "There were no signs. No real signs," he tells PEOPLE, and says that his son "had been clean for several years."
Though Frank had to lay his son to rest last month, he is grateful that he got to say goodbye: "We had an amazing time with him at the hospital."
"We saw him every minute of every day while he was there. They kept him alive a little bit longer so that he could do the donations we're talking about," says Frank. "The hospital did say that he's donated more than they've ever seen because his internals were in phenomenal shape."
In the wake of his son's death, Frank says that "several" people "have gotten in touch with us already in complete thankfulness - and incredibly grateful and incredibly sorry for our loss, but unbelievably grateful that they're able to continue living. Clay would have been thrilled to know that."
While his son may no longer be here, Frank is grateful for the positive legacy that his son's life continues to leave.
"That's a good thing that came out of it," Frank says of his son's decision to donate his organs. "Clay would be thrilled that these people are now living because of him."
If you or someone you know is struggling, please call The National Suicide Prevention Lifeline at 1-800-273-8255, open 24 hours a day.
This article was originally published on PEOPLE.com