Developing.

Update:

Fans, including celebs and journalists, have begun tweeting their condolences.

https://twitter.com/AlyssCampanella/status/498968260134842369

https://twitter.com/ArianaGrande/status/498974282706198528

Update:

TMZ reported last month that Williams was in rehab for alcohol abuse at at Hazelden Addiction Treatment Center near Lindstrom, Minnesota.

Update:

His last tweet was a birthday shout-out to his daughter, Zelda:

https://twitter.com/robinwilliams/status/494989879340584960

Update:

Williams’ death and apparent suicide have now been confirmed by numerous mainstream media outlets. We have revised our headline accordingly. (The original headline said he was “reportedly” dead.)