Robin Williams
Sarah Michelle Gellar and a slew of other celebrities took to Twitter to mourn Robin Williams on Monday. Reuters

Oscar-winning actor Robin Williams was found dead in his home Monday morning in a tragedy that shocked his family, friends and Hollywood. Celebrities took to Twitter after the comedian’s death to mourn the star and share their grief.

Sarah Michelle Gellar, his "The Crazy Ones" costar, shared pictures of herself with the actor:

Minnie Driver, who worked with star on "Good Will Hunting," said her heart felt broken:

Comedian Steve Martin tweeted about the loss:

Sesame Street remembered Williams:

Kathy Griffin shared a photo with the actor:

Ellen DeGeneres was in disbelief:

Michael Ian Black sent his condolences to the family:

Joel McHale called Williams his hero:

Singer Kelly Clarkson was devastated: