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Jack Nicholson and Diane Keaton struck up a close friendship in the 1970s that endured throughout the years. The two got even closer when they both starred in the 2003 rom-com Something’s Gotta Give.

Now, a source tells Globe that the One Flew Over the Cuckoo’s Nest actor is devastated by the news of her death and is struggling with the fact that he never got to say goodbye.

“They really bonded on that movie,” the source says, referring to Something’s Gotta Give. “It was one of Jack’s last big hurrahs in Hollywood before he went into full-blown retirement and he couldn’t have asked for a better experience than working alongside Diane as well as Keanu [Reeves] and Amanda [Peet].”

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The source adds that the cast “all got along like a mini-family” and that the group “spent a good amount of time together off set.”

Inside Diane Keaton and Jack Nicholson's Friendship Before Her Death | Us Weekly

“Jack would confide in her and vice-versa,” the source continues. “They stayed in touch after and she was one of the few people in his world whom he felt he could fully open up to. He’s stunned and very upset over her passing. It feels like he’s lost a sister.”

Keaton died on October 11 at the age of 79. She is survived by her two children, son Duke, 25, and daughter Dexter, 29.

While the Annie Hall star never married, she had several high-profile relationships with men like Warren Beatty, Woody Allen and Al Pacino.