FDNY firefighter Billy Moon’s family says he always had a big heart. And now it’s pumping the gift of life into somebody else.

Billy’s widow, Kristina Moon, and his two children met Richard Grehl, who received Billy’s heart in a transplant.

Billy, a volunteer in the Islip Fire Department, died following a training accident at his FDNY firehouse in Brooklyn.

The family used stethoscopes to hear Billy's heart in Richard's chest.

"It’s almost like when you hear your baby’s heartbeat for the first time. Hearing his heartbeat again it was really emotional," says Kristina Moon.

Expressing his gratitude, Richard said, "We were told it was a perfect heart. And it really is. It’s still perfect. I’ll take good care of it."

Billy Moon's organs saved the lives of five people.