OAKLAND (KPIX) — Watching Arthur Reyes cross the stage to receive his nursing degree, you’d never know that, not so long ago, he himself was a patient — on his death bed — after nearly five years suffering congestive heart failure.

He was hooked up to machines that pumped blood for him and waiting for a heart transplant donor.

“You’re hoping and praying that you get a call and hearing there was a donor was exciting but also bittersweet, because we know for heart transplant that it has to be someone who passed away,” Reyes remembers.

That someone in Reyes’ case was Justin Olivera, who died in a motorcycle accident in 2010.

Three years after the transplant, Olivera’s mother, Mary Knauer, wrote a letter to Reyes.

“He told me the first night we met, he said ‘this heart and I will do great things.’ And I believed him,” Knauer said.

At the graduation ceremony at Samuel Merritt University, Mary Knauer was there to cheer on the man whose heart was once her son’s.

“My son lives on right there,” she said with pride.