Darren Criss announces in a heartbreaking letter that his father has died

Darren Criss is mourning the death of his father, who passed away on Sunday.

"The American Crime Story" star posted a heartbreaking letter that paid tribute to his father, Charles William Criss Jr.

Criss shared numerous photos of his dad, including some of when he was younger and some of him celebrating some of Criss's biggest moments, along with the caption "Charles William Criss, Jr. May 1941 - April 2020."

The 33-year-old also included a moving letter to honor his father's legacy, writing, "Bill Criss has left the building."

The "Glee" alum went on, "After many years of coping with a rare heart condition - which, true to his form, very few would have ever been aware of - he finally checked out peacefully yesterday morning, surrounded by his loved ones."

Criss continued, "Dad lived an extraordinary life. Anyone who ever met Bill Criss adored him instantly. He could talk to anyone about anything."

Calling his father "deliriously charming" and "relentlessly selfless," he went on to reveal just how much his father shaped his career and life.

"He was a true gentleman through and through, and was a constant source of joy and inspiration for me. I've spent most of my life trying to be like him, wanting to see and do all the incredible things he did - and I am so grateful he was around to see me actually pull a few off," he detailed.

Criss was incredibly thankful that his father had been at his side "for all the greatest moments of my life, which of course, he always dressed up for."

Celebrities such as Ricky Martin, Gavin Degraw, Steve Aoki and many more reached out to Criss with their heartfelt condolences.

Charles William Criss Jr. leaves behind his wife Cerina Bru, his sons Darren and Chuck Criss, and his grandchildren.