Robin Williams
Robin Williams gestures during a panel discussion for his upcoming HBO show "Robin Williams: Weapons of Self-Destruction" at the Television Critics Association Cable summer press tour in Pasadena, California in this file picture taken July 30, 2009. Oscar-winning actor and comedian Williams was found dead on Monday from an apparent suicide at his home in Northern California, Marin County Sheriff's Office said. He was 63. Reuters/Mario Anzuoni/Files

Robin Williams’ last social media post was for his daughter. The 63-year-old Oscar winner greeted his daughter Zelda Rae Williams a happy 25th birthday in July.

Williams was found dead around noon on Monday at his California residence. Officials suspect it was suicide by asphyxiation, although investigation is still in progress.

Read: Robin Williams Dead in Apparent Suicide

His last known public message was for his daughter, who celebrated her 25th birthday on July 31.

“#tbt and Happy Birthday to Ms. Zelda Rae Williams! Quarter of a century old today but always my babi girl. Happy Birthday @zeldawilliams Love you!” the proud dad wrote on Instagram.

Click here to see the picture.

A few days prior, he appeared happy as he posted a photo of himself with a monkey named Crystal.

“Happy Birthday to me! A visit from one of my favourite leading ladies, Crystal,” the Instagram message read on July 21.

Williams was said to be suffering from depression before his death. He had been in several rehab centres over the years to treat his drugs and alcohol addiction.

His widow, Susan Schneider, opened up about her loss.

“This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings. I am utterly heartbroken. On behalf of Robin’s family, we are asking for privacy during our time of profound grief. As he is remembered, it is our hope the focus will not be on Robin’s death, but on the countless moments of joy and laughter he gave to millions,” she said in a statement to THR.

Read: Robin Williams’ Widow Susan Schneider Speaks Up; Plus Celebrities React on His Death

Williams is survived by Susan and his three children, Zelda, Zak and Cody.

U.S. President Barack Obama expressed his condolences to the family of the great Hollywood star.

“Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between. But he was one of a kind. He arrived in our lives as an alien – but he ended up touching every element of the human spirit,” the leader said.

“He made us laugh. He made us cry. He gave his immeasurable talent freely and generously to those who needed it most – from our troops stationed abroad to the marginalised on our own streets. The Obama family offers our condolences to Robin’s family, his friends, and everyone who found their voice and their verse thanks to Robin Williams.”

Here are some more celebrities who have expressed their grief over Williams’ death.

His heart was as big as his genius. So sad. Rest in Peace Robin Williams.

— bob saget (@bobsaget) August 11, 2014

The Robin Williams news is devastating. I feel sick. — Michael Ian Black (@michaelianblack) August 11, 2014

RIP @robinwilliams You were one of the very best that ever was. You were one of my heroes. #RobinWilliams

— Joel McHale (@joelmchale) August 11, 2014

No! Robin Williams you were so loved. — mia farrow (@MiaFarrow) August 11, 2014

I could not be more stunned by the loss of Robin Williams, mensch, great talent, acting partner, genuine soul.

— Steve Martin (@SteveMartinToGo) August 11, 2014

Robin Williams made the world laugh & think. I will remember & honor that. A great man, artist and friend. I will miss him beyond measure. — Kevin Spacey (@KevinSpacey) August 12, 2014

I am stunned and just reeling from the news of Robin Williams' death. He brought so much joy and heart to millions... Just, wow.

— Neil Patrick Harris (@ActuallyNPH) August 12, 2014

The U.S. Air Force quoted Williams from his 1987 film “Good Morning, Vietnam,” which earned him an Academy Award for Best Actor nomination.

"Gooood morning Vietnam! It's 0600 hours. What does the "O" stand for? O my God, it's early!" #RobinWilliams as Airman Cronauer. #USAF #RIP — U.S. Air Force (@usairforce) August 12, 2014