The 50-year-old actor, who met Williams on Saturday Night Live, believes a Parkinson's drug could have played a role in his friend's passing.
"Now that we can talk about it. #RobinWilliams was on a drug treating the symptoms of Parkinson's," he tweeted. "One of the SIDE-EFFECTS IS SUICIDE!"
He added, "The Evil pharmaceutical industry ADMITS TO OVER 100,000 people in the USA DIE A YEAR FROM "PRESCRIPTION" DRUGS!! #RobinWilliams"
According to the Marin County Sheriff's Department, Williams died from asphyxia due to hanging. The comedy legend was 63.
His wife, Susan Schneider, later revealed the actor was battling early stages of Parkinson's Disease before his passing. It is not clear whether or not Williams was on any medication for the condition.
According to the MIchael J. Fox Foundation for Parkinson's Research, "available drugs can greatly enhance the quality of life of a Parkinson's patient." They also say it's essential to work closely with a doctor and all medical caregivers involved with your treatment regimen to develop the approach that's right for you.
Dr. Benjamin Walter, who serves as director of the Movement Disorders Center at University Hospitals Neurological Institute, echoes those statements. "Anti-depressants may have a role [in depression], but that is complicated and not as effective as we'd like it to be," he told Cleveland.com. Walter has never treated Williams.
Regardless of Williams' physical and mental health, Schneider will always remember Williams for his talent and charisma.
"If you were ever so lucky as to see Robin Williams live…You have a story to tell your Grand Kids!" he Tweeted. "#RobinWilliams was our Elvis!"
He added, "Just thank and hug the ones you love and who have touched your lives! Thx4ever #RobinWilliams."
If you or someone you know needs help, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).