When Robin Williams died, the entertainment world lost one of its brightest lights.
Now his widow, Susan Schneider Williams, is opening up about her late husband and the baffling disease that tormented him before he took his life.
Williams shares her story in the upcoming People and the ABC special "People Icons: Gone Too Soon" to try and ease the pain of those living with Lewy Body Dementia, a disease that causes disorientation and hallucinations, among other symptoms.
The Oscar winner died by suicide in August 2014 at age 63, but it was only after his autopsy that his family learned he was suffering with Lewy Body Dementia, a disease Williams described as "the terrorist inside my husband's brain" in an essay she wrote last year for the medical journal Neurology.
“The Robin that I knew was not the crazy, manic one who would be performing on stage for comedy or sometimes in his roles as an actor,” Williams said during the televised special's emotional interview.
Williams described her late husband as a "quiet, intellectual man" at home, someone who carefully observed others.
"If you can imagine the energy that he would bring to the stage — no one can do that full-time," she said. "And I think the brilliance behind that impact of energy he would bring was because in his time off, he was someone who was contemplative and an observational genius."
But her late husband's real "legacy," said Williams, will ultimately be to "shed light on brain disease as a whole, but particularly dementia, which 47 million people worldwide are suffering right now."
Above all, the beloved entertainer's death, she said, will allow others living with Lewy Body Dementia "to know that they are not alone, that this is what Robin Williams had and they’re being heard, they’re not outcasts."
"People Icons: Gone Too Soon" airs Tuesday at 10 p.m. ET on ABC.