The comedian spoke with ET's Nischelle Turner at the Hollywood premiere of HBO's new documentary, Robin Williams: Come Inside My Mind, on Wednesday, where he had a hard time fighting back tears as he emotionally reflected on the impact the iconic actor had on his life and his career.
"Oh, you're killing me, you're killing me," Saget said as he began to get emotional while explaining how Williams' untimely death in 2014 left "a huge chasm in everybody's life."
"[He was] a whirlwind of energy a beautiful human being," Saget said, solemnly. "[It was] a giant loss. Everybody felt it."
"In 1978, I moved to L.A. went to the Comedy Store, met Robin right away, he had just finished with Rowan and Martin's Laugh-In [and] it was before Mork and Mindy, and he just liked me and my act," Saget shared, recalling the start of their life-long friendship.
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The Full House alum also praised Williams for his generosity and dedication to helping others, explaining how the iconic star volunteered to perform at seven different benefit galas for the Scleroderma Research Foundation -- which Saget is closely involved with.
"We raised $46 million in those years for research because of Robin. That's how philanthropic he was," Saget shared.
Looking back at the breadth of Williams' impressive career, Saget couldn't help but marvel at his immense versatility.
"If he had never been a stand-up, which would have been a loss for everybody, if he'd just done the movie parts that he did, [like] Mrs. Doubtfire, Goodwill Hunting, you'd go, 'My God, what a genius actor!'" he said. "This is a man that was a force that you don't see [but] every couple hundred years."
The 62-year-old comic continued to fight back tears as he admitted that it's still hard for him to refer to Williams in the past-tense, with words like "was," and looked back on one of his favorite memories.
"There's one time when I was in the Comedy Store in La Jolla [California], and he was there and I was feeling bummed out about my career and he said, 'Hey come in here.' And we went in the dressing room and we watched TV with the sound off and just made up words," Saget remembered. "He liked funny people. He could tell when someone was talented and he wanted to know all about them and work them, figure them out. And he was beloved and he was special."
HBO's Robin Williams: Come Inside My Mind reveals an intimate look into the tumultuous, brilliant and complex life of the beloved comic, who died of suicide in August 2014 at age 63. The documentary premieres on July 16.