Losing a coworker who you spent several years with can be especially heartbreaking. Mark Harmon and David McCallum spent several years together working on NCIS.

The news of David McCallum’s death has, of course, impacted the actor immensely, and he broke his silence and said some words about it. Keep reading to learn what Harmon said of his beloved former co-star.

David McCallum’s death has broken hearts all over the world. The actor was loved for his role as Dr. Donald ‘Ducky’ Mallard on NCIS. And for several years, he graced viewers’ screens and played the role with the utmost conviction.

He made a home in the hearts of every fan who watched the show. McCallum’s death was confirmed to Fox News earlier this week in a statement that revealed he passed away of natural causes at New York Presbyterian Hospital.

“David was a gifted actor and author, and beloved by many around the world. He led an incredible life, and his legacy will forever live on through his family and the countless hours on film and television that will never go away,” the statement read.

McCallum is survived by his wife of almost 60 years, Katherine Carpenter, and his five children (from a prior marriage as well as from his marriage to Carpenter), as well as eight grandchildren.

After the news of his death hit the public, tributes began rolling in. NCIS‘ current exec producers, Seven D. Binder and David North made a statement expressing their heartfelt grief at the loss.