On August 11, 2014, at his home in Paradise Cay, California, Williams committed suicide by hanging. His body was cremated at Monte's Chapel of the Hills in San Anselmo, and his ashes were scattered over San Francisco Bay the next day.
The final autopsy report, released in November 2014, concluded that he "died of asphyxia due to hanging". Neither alcohol nor illegal drugs were involved, and prescription drugs present in his body were at therapeutic levels. The report also noted that Williams had been suffering from depression and anxiety. An examination of his brain tissue suggested Williams suffered from "diffuse Lewy body dementia". Describing the disease as "the terrorist inside my husband's brain", his widow Susan Schneider Williams said that "however you look at it—the presence of Lewy bodies took his life", referring to his previous diagnosis of Parkinson's. She revealed that in the year before his death Williams had experienced a sudden and prolonged spike in fear and anxiety, depression, and insomnia, which worsened in severity to include memory loss, paranoia, and delusions. Medical experts struggled to determine a cause, and eventually diagnosed him with Parkinson's disease.
At the United Nations Headquarters on August 12, 2014, Robin Williams was celebrated during the opening of the International Youth Day. In the presence of U.N. Secretary General Ban Ki Moon, Assistant Secretary General Thomas Gass paid tribute to Williams by standing on the pulpit of the ECOSOC Chamber and quoting Keating's lines from the 1989 film Dead Poets Society: "Dare to look at things in a different way!" Several fans similarly paid tribute to Williams on social media with photo and video reenactments of Dead Poets Society's "O Captain! My Captain!" scene.
During the 66th Primetime Emmy Awards on August 25, 2014, close friend and fellow comedian Billy Crystal presented a tribute to Williams, referring to him as "the brightest star in our comedy galaxy". Afterwards, some of Williams' best comedy moments were shown, including his first ever The Tonight Show appearance, indicating his great life in making people laugh. Talk show hosts including David Letterman, Conan O'Brien, Seth Meyers, Jimmy Kimmel, and Jimmy Fallon paid tribute to Williams on their respective shows.
On September 9, 2014, PBS aired a one-hour special devoted to his career, and on September 27, 2014, dozens of leading stars and celebrities held a tribute in San Francisco to celebrate his life and career.