'90 Day Fiancé' Breakout Star Chuck Potthast Dead at 64

"90 Day Fiancé" star Elizabeth Castravet announced the death of her father, Chuck Potthast, in an Instagram post Sunday.

The reality television star wrote her father died two weeks ago and her family's been "completely shattered."

One of Elizabeth's sisters, Rebekah Lichtwerch, also paid tribute to her late father on Instagram, writing her world has been "distorted into a place I don’t understand."

Chuck Potthast -- who appeared in several episodes of "90 Day Fiancé: Happily Ever After?" -- had been open about his struggles with his health ... in one episode of the show, he urged his daughter to patch up her differences with family members.

His family has not yet released the cause of his death.

Chuck posted a health update on Instagram in September, revealing he underwent an 8-hour surgery to repair a hernia and a collapsed stomach.

Chuck took the surgery in stride and jokingly pointed out the procedure left him with a flat stomach.

Chuck Potthast was 64 years old.