The "Friends" Cast and Other Stars React to Matthew Perry's Death: "So Utterly Devastated"

The "Criminal Minds" star — who guest-starred during season four of "Friends" — paid tribute to Perry on X, writing, "I'm so very sad to hear about @MatthewPerry. He was lovely to me on Friends and every time I saw him in the decades after. Please read his book. It was his legacy to help. He won't rest in peace though.. He's already too busy making everyone laugh up there."