Los Angeles: In a moving tribute to close friend Robin Williams, `Late Night` host David Letterman said like everyone else he had no idea that the actor-comedian, who committed suicide recently, was in so much pain.
Letterman dedicated a section of the show to remember Williams, whom he first met 38-years ago.
"I knew Robin Williams for 38 years - 38 years, which in of itself is crazy how time...," Letterman said, adding, "more questions are raised than can possibly be answered" by Williams suicide on August 11.
"What I will add here is beyond being a very talented man, and a good friend and a gentleman, I`m sorry, like everybody else, I had no idea that the man was in pain, that the man was suffering," Letterman said.
He also paid tribute to Williams talent and said his spark made many of them insecure.
"All of a sudden he comes up on the stage and - you know what it is - it`s like nothing we had ever seen before, nothing we had ever imagined before.
"And then he finishes and I thought, `Oh that`s it, they`re gonna have to put an end to showbusiness because what could happen after this?` Honest to God you thought, `Holy crap, there goes my chance in show business because of this guy`," Letterman recalled.
The popular host revealed that Williams helped him in the intial days of his career by securing roles for him on hit show `Mork & Mindy` besides making appearances as a guest on his show many times.