The 44-year-old British actress had starred with the actor in Good Will Hunting, the movie that garnered him his first and only Oscar. Driver, who now appears on the NBC show About a Boy, made her comments to E! News at the Hollywood Foreign Press Association Installation Dinner in Beverly Hills on Thursday.
Three days earlier, Robin was found dead at his home. He was 63. Authorities confirmed he had taken his own life. The actor, known best for his high-energy performances, had suffered from depression and his wife, Susan Schneider, recently revealed that he had also been diagnosed with Parkinson's disease, which affects the mind and body and has no cure.
"It was a very hard day. It was a hard day at work, I gotta say," Driver said. "I was utterly shocked. I think that's a great testament to who he was as a person 'cause everybody knew that he...had some darkness. But you never saw that. I'm sure his family did, but [to] his friends and the people that worked with him, he was one of the funniest, best, loveliest people to be around."
In the 1997 film Good Will Hunting, the actor played a therapist named Dr. Sean Maguire who treats the main character, troubled genius Will Hunting, played by Matt Damon. Williams won the Oscar for Best Actor in a Supporting Role, while Damon and co-star Ben Affleck won their first Oscars for the film as well—for co-writing its screenplay. Williams was also nominated for Oscars for his roles in Dead Poet's Society, The Fisher King and Good Morning, Vietnam.
Driver, who received an Academy Award nomination for her role as Hunting's love interest, Skylar, was one of many celebrities who took to Twitter to express sympathy and shock over Williams' death. Damon said in a statement that Williams brought "so much joy" into his life.
Soon after learning about the actor's death, scores of fans flocked to memorialize him at the house featured on Mork and Mindy, the 1970s sitcom that marked his breakout onscreen role, and beside a bench he sat on during an iconic scene in Good Will Hunting (see photos). Watch the video above to find out what Driver had to say about it.