"John Henry Matthew Reilly AKA Jack. The brightest light in the world has gone out. Imagine the best person in the world. Now imagine that person being your dad. I'm so grateful he was mine. I'm so grateful I got to love him. I'm so grateful I made it in time to hold him and say goodbye," Caitlin wrote in the caption of a photo of her and her dad. "I honestly don't know what I'm going to do, but I know he'll be with me. I love you forever Daddy."
John began a prolific TV career in the '70s, where he guest starred on shows like The Mary Tyler Moore Show, Wonder Woman and How the West Was Won. Beginning in 1984, he starred on General Hospital as WSB agent Sean Donely. In 1994, he left the show after choosing not to renew his contract, according to People.
Following his time on General Hospital, he appeared as Del Douglas on Sunset Beach and Alistair Crane on Passions.
He also went on to act alongside Jennie Garth on Beverly Hills, 90210 as Kelly Taylor's father.
John returned to his soap opera roots to appear as his character on General Hospital: Night Shift in 2013. He also appeared on the Emmy Award-nominated Amazon Prime drama series The Bay in 2012.