Mark Harmon, who played Special Agent Leroy Jethro Gibbs, has officially left "NCIS" after his last episode aired on Monday. Fans have been speculating about Gibbs' future retirement for months and are now wondering who will replace him as the leader of the Naval Criminal Investigative Service. While it is uncertain if Harmon will ever return to the show, showrunner Steven D. Binder stated that Mark will always be an integral part of the show, and anything could happen in the future.
