Robin Williams

Beloved comic and Oscar winner Robin Williams died Monday at the age of 63. Williams died of a suspected suicide, according to a statement from authorities in Marin County, Calif., where Williams was found dead.

Robin Williams dies of suspected suicide at 63

In the wake of the tragic news, many celebrities, fellow comedians and co-stars took to Twitter to mourn Williams' passing:

Gellar later added in a statement to People: "My life is a better place because I knew Robin Williams. To my children he was Uncle Robin, to everyone he worked with, he was the best boss anyone had ever known, and to me he was not just an inspiration but he was the Father I had always dreamed of having. There are not enough adjectives to describe the light he was, to anyone that ever had the pleasure to meet him. I will miss him everyday, but I know the memory of him will live on. And to his family, I thank them for letting us know him and seeing the joy they brought him. Us crazy ones love you.

"God, grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference."

If you or someone you know needs help, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).