NCIS star Mark Harmon pays tribute to his co-star David McCallum, who passed away at the age of 90. McCallum was the last original cast member of the show and played Chief Medical Examiner Donald "Ducky" Mallard for two decades. Harmon describes McCallum as having lived a great life and expresses his condolences to McCallum's family. The executive producers of NCIS also released a statement honoring McCallum, describing him as a scholar, gentleman, and legend who will be greatly missed. CBS also pays tribute to McCallum, highlighting his talent, warmth, and sense of humor.