Emotional Billy Crystal shares his final moments with Rob Reiner

Billy Crystal is getting vulnerable about how he's processing the death of close friend Rob Reiner.

"There's so many moments that when something good happens, or [I think] 'Isn't that crazy?' I want to pick up the phone and call [him] and say, 'Did you see it?' Because that's what we would do," the 78-year-old actor said during his April 14 appearance on "The Late Show with Stephen Colbert."

Crystal remembered his "When Harry Met Sally …" director, who died at 78 alongside wife Michele Reiner in a suspected double homicide in December, as "hilarious, devoted, opinionated in the best way, fighting for the truth for our country."

"We could talk about everything. He was an uncle to my kids," Crystal told Colbert.

The "City Slickers" actor, who is promoting his upcoming one-man show on Broadway, also opened up about his final conversations with Reiner during Oscars host Conan O'Brien's Christmas party the night before the Reiners' killings.

Crystal appeared to get choked up at the top of the interview, when Colbert asked about the ensemble tribute to Reiner during the Oscars last month.

"I know it must be a very difficult thing to talk about because he was such an incredible friend to you, such an incredible artist, beloved by so many, and [the Reiners' deaths] came in such a shocking and terrible way," Colbert said after Crystal struggled to find words for several seconds.

"No, I'm good. It was shortly after the tragedy. We had spent the night before together and talking about our careers together," Crystal said. "We were talking about the movie business and how it's changed, and how people don't go to theaters like they used to. And we talked about the fact that you can't control how a movie is gonna do."

"What you can control is the experience of making it. And the experiences that we had together and that he had with the casts of his other movies was so extraordinary. He said that's something you always have," he continued. "Hits are great to have, but it's the people that you hold on to."

Rob Reiner's Oscars tribute would have 'made him really smile'

It was this philosophy that inspired Crystal to start coordinating a special moment for Reiner during the Oscars telecast.

Crystal and his "When Harry Met Sally" costar Meg Ryan were joined onstage by Demi Moore, John Cusack, Cary Elwes, Mandy Patinkin, Kiefer Sutherland, Kathy Bates, Annette Bening, Daphne Zuniga, Michael McKean, Christopher Guest, Jerry O'Connell, Wil Wheaton, Fred Savage, Kevin Pollack and Carol Kane.

"If I can get the casts of those movies together to walk out with me, that [would] have made him really smile," Crystal said. "So I got in touch with all of them."

Reiner and Crystal were frequent collaborators after Crystal appeared on "All in the Family" in 1976 as Mike's (played by Reiner) friend Al. "The Princess Bride" and "This Is Spinal Tap" were among their other film collaborations.

Michele and Rob Reiner's 32-year-old son, Nick Reiner, is being held in jail without bail after pleading not guilty to murdering his parents.

The Reiners' deaths remain under investigation; in a Dec. 14 news conference, the Los Angeles Police Department said "many family members" would be interviewed throughout the process. Police have released scant details about the alleged homicide, including the couple's injuries.