Yes it's true. He's passed away at the age of 63. And while we won't specifically comment on the situation behind his death because of its tragic and complicated nature, we will say that he'll be sorely missed.
He previously mentioned being a fan of the Zelda series too, which just makes commercials like this just the more depressing in hindsight:
https://www.youtube.com/watch?v=IgjHrrNVBks
RIP Mr Williams. Our condolences go out to your family and others impacted by your passing.
Just found out a few minutes ago too. He was a funny guy and I remember he went on / or rather was on Ray William Johnson. And I had absolutely no idea there was an ad linking him with the Legend of Zelda :o , well, you will be missed. ):
His death really saddens me, ... as he was a genuinely funny, sweet man. It just shows that money and fame can't bring you happiness. I finished watching Mrs. Doubtfire today, never seen it before but really really enjoyed it.