Susan Williams, the widow of comedian Robin Williams, is speaking out for the first time since her husband's suicide on August 11, 2014, in their Tiburon, California, home.
Susan told ABC News on Nov. 3 that her 63-year-old husband was planning to check himself into a medical facility for neurocognitive testing on the week of his suicide.
On August 11, Susan said she left for work thinking her husband was asleep in another room, but later that morning, she learned the truth from Robin's assistant and rushed home.
“And I got to tell him, ‘I forgive you with all my heart. You're the bravest man I've ever known,’" Williams stated. "You know, we were living a nightmare.”
Susan said her husband started experiencing different symptoms beginning in November 2013, but they couldn't figure out what the main cause was.
In May 2014, Robin was diagnosed with the early stages of Parkinson's Disease. She recalled how he smashed his head badly in July 2014.
What Susan, Robin and his doctors did not know was that the actor was suffering from Diffuse Lewy Body Dementia, also known as Dementia with Lewy bodies (DLB), which was discovered during an autopsy.
DLB is a neurodegenerative dementia disease that causes hallucinations, anxiety attacks, problems with motor skills and delusions.
Susan said that Robin tried to keep it together, but "the dam broke" during the last month of his life.
"It was not depression that killed Robin," Susan told PEOPLE in a separate interview. "Depression was one of let's call it 50 symptoms and it was a small one."
"[The symptoms] present themselves like a pinball machine," Susan said. "You don't know exactly what you're looking at."
"I know now the doctors, the whole team was doing exactly the right things," Susan added. "It's just that this disease was faster than us and bigger than us. We would have gotten there eventually."
She recalled that "one of the doctors said, 'Robin was very aware that he was losing his mind and there was nothing he could do about it.'"