In an exclusive conversation with PEOPLE ahead of theNCIStribute episode to McCallum, airing Monday night, Dietzen, 46, reflects on the last conversation he had with the late actor a few days before his death.
“I’ll say that I got to speak to him on his birthday, which was wonderful,” he says. “That was on a Tuesday. He ended up passing away that weekend, so he was already in the hospital and obviously not doing very well.”
Brian Dietzen and David McCallum on ‘NCIS’.Monty Brinton/CBS via Getty

Monty Brinton/CBS via Getty
Dietzen shares how McCallum’s wife, Katherine, passed the phone to him in his hospital bed. He adds thatThe Great Escapestar was “very coherent” and Dietzen was “very happy to hear it.”
“He was, obviously, going through some health issues and whatnot, but he had this stretch of time in that last week where he got to chat with all of his family, his kids, and obviously, Katherine,” he continues. “And I was lucky enough that when I called in, I got to actually talk to him.”
Although he plans to keep the “contents of the call” just between them, Dietzen adds, “I will say I’m so glad that I got to speak to him one last time and I got to tell him how I felt. And so that was really meaningful.”
David McCallum.Sonja Flemming/CBS

Sonja Flemming/CBS
After studying at the Royal Academy of Dramatic Arts and doing several years in repertory theater in the United Kingdom, the Scotland-born actor moved to America in 1961. He landed the role of Illya Kuryakin inThe Man from U.N.C.L.E.opposite Robert Vaughn. He earned two Emmy and a Golden nomination for the role. After joiningNCISin 2003, McCallum became best known for playing Dr. Donald “Ducky” Mallard on the crime series.
NCISwill honor McCallum’s legacy with a special episode on Monday. Dietzen, who plays the protégé of his character Ducky, was tasked with co-writing the tribute with executive producer Scott Williams.
David McCallum, Emily Wickersham and Mark Harmon on ‘NCIS’.Sonja Flemming/CBS via Getty Images

Sonja Flemming/CBS via Getty Images
“I think everyone in their own way was mourning this loss,” he continues. “And I think that Scott Williams and I both had to recognize that we didn’t want this show to fall into, well, this is just going to be forty-two minutes of us mourning and crying. There has to be a celebration about this.”
Dietzen explains that he wanted to convey that not only has theNCISuniverse benefitted from McCallum, but also how the “artists and humans outside of the show” have become “better for having known this awesome person.”
Francis Specker/CBS via Getty, Kristina Bumphrey/Starpix/Shutterstock

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NCISairs Mondays at 9 p.m. ET on CBS.
source: people.com