Chrishell Stause is remembering her late co-star Billy Miller.

Over the weekend, it was announced that Billy, best known for his roles on soap operas including The Young and the Restless and General Hospital, had passed away at the age of 43 on Friday, September 15).

Billy‘s manager shared in a statement with People that he had been “struggling with manic depression when he died.” No specific cause of death was cited.

Chrishell, 42, worked with Billy when he joined All My Children in 2007 as Richie Novak, which he played until 2008. She played Amanda Dillon from 2005 to 2011.

On what would have been Billy‘s 44th birthday on Sunday (Sept. 17), Chrishell paid tribute to her “friend.”

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“Still processing this. Too many feelings, but you are gone way too soon and I’m so happy I got to work with you all those years, but also call you a friend,” Chrishell wrote on her Instagram Story.

“I hope you are at peace now,” Chrishell added, along with a photo of Billy giving her a kiss on the cheek on a red carpet.

Our thoughts are with Billy Miller‘s loved ones at this incredibly difficult time.