Elton John and Madonna, two close friends of the late artist George Michael, are paying tribute to the singer after his shocking death on Christmas Day.

The singer died at the young age of 53 on Sunday (December 25). He died “peacefully” in his sleep and was discovered dead at his home.

Elton and George famously collaborated on the song “Don’t Let the Sun Go Down on Me” in 1991. They topped both the U.S. and U.K. charts together with the hit.

“I am in deep shock. I have lost a beloved friend – the kindest, most generous soul and a brilliant artist. My heart goes out to his family, friends and all of his fans,” Elton wrote on Instagram.

Madonna paid tribute to George by sharing the clip of her presenting the Video Vanguard Award