Michael J. Fox, who has been openly living with Parkinson’s Disease since 1998, had not known that his friend Robin Williams was in the early stages of the disorder.

Michael J. Fox On Robin Williams' Parkinson's

After news broke that Williams had been diagnosed with Parkinson’s Disease sometime before he took his own life, Fox took to Twitter to express his surprise that his friend was afflicted with the disorder he’s long fought. Fox also noted that he believed Williams had lent his support to his Parkinsin’s foundation before he found out about his own health.

Stunned to learn Robin had PD. Pretty sure his support for our Fdn predated his diagnosis. A true friend; I wish him peace.

— Michael J. Fox (@realmikefox) August 14, 2014

Fox had previously used Twitter to pay his respects towards Williams like countless others who lauded the late actor for both his talents and his kindness.

Famously kind, ferociously funny, a genius and a gentle soul. What a loss. #RobinWilliams

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— Michael J. Fox (@realmikefox) August 12, 2014

Williams’ wife Susan Schneider released a statement on his passing on Thursday. Likely in an effort to turn the speculation away from the possibility that Williams had fallen off the wagon before his death, Schneider stated that her husband had been sober, but had been dealing with “depression, anxiety as well as early stages of Parkinson’s Disease.”

Williams was found dead in his home of an apparent suicide on Monday, Aug. 11. He was 63.