Author Daniel Keyes who wrote books like the "Flowers for Algernon," "The Minds of Billy Milligan" and "Unveiling Claudia: A True Story of Serial Murder" has died at the age of 86.

Keyes' daughter Leslie confirmed the news of her father's passing on Sunday, saying that the death was caused by complications from pneumonia.

"Flowers for Algernon" became a famous novel among students who wanted to learn how to address mental disability and the importance of human intelligence.

The book is focused on the life of a man with a below average IQ, but who later on becomes a genius temporarily following a surgery, The Globe and Mail reported.

In a memoir he wrote in 1999 entitled "Algernon, Charlie and I," Keyes explained how he came up with the idea for the book. As a young boy, Keyes' parents always wanted him to become a doctor, but he knew he wasn't meant for that kind of profession, according to the Daily Mail.

"I thought: My education is driving a wedge between me and the people I love. And then I wondered: What would happen if it were possible to increase a person's intelligence?"

Fifteen years later, "Flowers for Algernon" came to life and has gained him the prestigious Hugo Award for Best Short Fiction in 1960.

In the same year, Keyes' short fiction has expanded into a novel and received the Nebula Award for Best Novel in the same year.

Eight years after, "Flowers of Algernon" became a critically acclaimed film that starred Cliff Robinson and earned the actor an Academy Award.

In an excerpt from the book, Keyes as Charlie wrote, "Don't feel sorry for me. I'm glad I had a second chance in life like you said to be smart because I learned a lot of things that I never knew were in this world and I'm grateful I saw it even for a little bit," USA Today noted.