When news broke that David McCallum, the beloved actor who portrayed Dr. Donald “Ducky” Mallard on NCIS, had passed away, longtime co-star Mark Harmon was deeply saddened by the loss of a man he had worked beside for nearly two decades.

Harmon reportedly reflected on McCallum not only as a talented actor but as a kind, intelligent, and generous friend who brought warmth and wisdom to the set every day. He shared that David’s presence helped shape the heart of NCIS, and his quiet humor and professionalism made him admired by everyone who knew him. Harmon expressed that while McCallum’s passing left a profound emptiness, his legacy through the show, his unforgettable characters, and the memories shared with cast and fans would never fade.