George Michael‘s Wham! bandmate Andrew Ridgeley expressed his grief following the singer’s death. Ridgeley took to Twitter to share a tribute to his friend.

“Heartbroken at the loss of my beloved friend Yog,” Ridgeley wrote on Christmas night.

The world was shocked by the news that 53-year-old Michael was found dead in his apartment on Christmas Day. The cause of death is said to be heart failure.

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On Monday, Ridgeley, who had remained close to his bandmate of Wham!, continued his remembrance of Michael, tweeting “#GM had a voice that would transport u, he was the finest singer/songwriter of his generation & has left the best of himself 4 us.”

RIdgeley has stayed out of the public eye since Wham! disbanded. He is involved in numerous charities, including charities for clean water and education.