It has been more than 4 years since the death of prolific actor and comedian Robin Williams. His death at the age of 63 was a huge loss for his wife Susan Schneider Williams, his children, people who knew and loved him, as well as his fans.

In an essay titled, "The terrorist inside my husband's brain", Robin's wife shared the sad story of how the "little-known but deadly Lewy body disease (LBD)" made her husband frustrated with the confinement within his own head. He was suffering from endless confusion, from anxiety and losing sleep, as well as period of impaired decision making.

Prior to his death, Robin Williams already realized that something was not right with his mind. At first, he was misdiagnosed because his brain disease is a difficult disease to recognize. Lon Schneider, a psychiatry professor at the University of Southern California explained that, "at the beginning it subtly affects the way we think, and it subtly affects the way we're able to move so we don't recognize this illness until it progresses.” The symptoms are also very similar to Alzheimer's, Parkinson's, and depression. Problems with paranoia, delusions, looping, insomnia, memory, and high cortisol levels got worse as his final days approached. Susan recalled that he kept saying, “I just want to reboot my brain.”

During the filming of Night at the Museum: Secret of the Tomb in 2014, the Oscar-winning actor struggled with remembering his lines. His makeup artist, Cheri Minns, recalled that, "He was sobbing in my arms at the end of every day. It was horrible. Horrible," and there was nothing she could do to help him deal with that was happening to him.

Schneider describes the avalanche of symptoms: “It was like playing whack-a-mole. Which symptom is it this month? I thought, is my husband a hypochondriac? We’re chasing it and there’s no answers, and by now we’d tried everything.” People who were around Robin William, like producers and colleagues, all noticed that he dropped weight, his once booming voice became tremulous, and he stooped. He tried treatments, he got back into rehabilitation with the hope to improve, but brain disease is not like any other addiction or affliction.

He couldn't return to his standup comedy roots as he used to, because he didn't know how anymore. A once funny man was crying while saying that he no longer knew how to be funny, although he certainly tried. He attended comedian Mark Pitta's show in 2014 much to the delight and awe of many people. In the green room, he didn't miss a beat when it came down to a joke.

His last days weren't as pleasant. His loved ones remember his bizarre actions, such as stuffing his watches into a sock and bringing things to his friends for safe keeping. Everyone was worried, but nobody knew what to do. Even his wife found it difficult to provide her husband any form of comfort or reassurance. It came to a point where Robin couldn't bare it anymore and suicide was his way out. If it was not for the diagnosis of LBD three months after he hung himself, his wife Susan would probably be forever in distress.

A new book titled Robin will go on sale on May 15. In the biography, his wife, his previous makeup artist, and many others comment on how the legendary star went from being a boy with a privileged but lonely childhood, to becoming a drug addict, to acting and turning into one of Hollywood's brightest stars. It will also tell the story of a fighter who tried his best to live with an incurable brain disease.