One of the first to pay respect to the late actor was John Travolta, who recalled their Broadway experiences in the musicals Grease and Over Here.

“Treat Williams, and I got our start together in NYC appearing in two Broadway shows, Grease and Over Here,” he writes.

“Treat, I’m so sorry. I’m thinking of you and your family. We will miss you. Love, John.”

Williams and Catherine Zeta-Jones co-starred in the 1996 film The Phantom, and Zeta-Jones tweeted a still from the film with the simple caption “R.I.P. Dearest Treat Williams.”

“I’m in shock!,” tweeted Kim Cattrall, who co-starred with the deceased actor and father of two in the 1999 television film 36 Hours to Die.

“Goodbye, Dear Treat. Pam, Gille, Ellie, and the family have my condolences. A great buddy and actor.”

With a screenshot of a news article announcing his passing, Sharon Stone wrote: “Sad news, rest in peace, brother.”

The actress who played Williams’ co-star in the film Everwood, Emily VanCamp, shared a photo of the actor in his youth and said, “The many times we worked together was always amazing and I was always enthusiastic for the next time. I’m sending your family my entire love, Treat. Take off, my friend.”

As an uncredited storm base warrior with him in The Empire Strikes Back (1980), Mark Hamill posted a picture of them from the set and captioned it, “Just got the horrible news that the world has lost @Rtreatwilliams. Such a great individual, such a talented actor, and such a beloved friend. I’m crushed. #RIP_Pal.”

“Treat and I spent months filming Once Upon a Time in America in Rome,” recalled his co-star James Woods, who appeared alongside him in the 1984 epic crime drama.

“A long shoot may make it very lonely on the road, but his enduring good humor and sense of humor were a Godsend. He was someone I truly liked, and I’m crushed by his passing. #TreatWilliams, R.I.P.”

Billy Baldwin wrote a lengthy ode to the celebrity in which he gushed about how smart, talented, funny, charming, successful, handsome, and compassionate he was. “A golden heart.”

He added: “A horrible loss. He was a dedicated fighter for social justice and climate change. We will miss you. Treat, rest in peace.”