Susan and Robin Williams on the Happy Feet 2 red carpet

Robin Williams’ widow Susan is opening up to People about why Robin killed himself in August 2014 — it was after battling a debilitating, neurodegenerative disease called Dementia with Lewy Bodies (LBD).

DLB is the second most common dementia disorder after Alzheimer’s. It can cause hallucinations, impaired motor function and fluctuations in mental status. Susan describes “whack-a-mole”-like symptoms that started popping up on Robin out of nowhere, including heightened levels of anxiety and delusions.

“It was not depression that killed Robin. Depression was one of let’s call it 50 symptoms and it was a small one,” says Susan. “[The symptoms] present themselves like a pinball machine. You don’t know exactly what you’re looking.”

Williams’ doctors could not pinpoint what was wrong with him until his autopsy, though Susan does not blame them.

RELATED: Remembering Robin Williams, from ‘Dead Poets Society’ to ‘Mrs. Doubtfire’

“I know now the doctors, the whole team was doing exactly the right things. It’s just that this disease was faster than us and bigger than us. We would have gotten there eventually,” she says.

Susan adds that she’s going to work to help others who are affected by DLB, hoping to prevent more tragic loss of life from people who don’t understand what’s happening to them.

“I’ve spent this last year trying to find out what killed Robin. To understand what we were fighting, what we were in the trenches fighting and one of the doctors said, ‘Robin was very aware that he was losing his mind and there was nothing he could do about it,'” she says.

“This was a very unique case and I pray to God that it will shed some light on Lewy bodies for the millions of people and their loved ones who are suffering with it. Because we didn’t know. He didn’t know.”

Posted by:Andrea Reiher

TV critic by way of law school, Andrea Reiher enjoys everything from highbrow drama to clever comedy to the best reality TV has to offer. Her TV heroes include CJ Cregg, Spencer Hastings, Diane Lockhart, Juliet O'Hara and Buffy Summers. TV words to live by: "I'm a slayer, ask me how."