According to Wikipedia,
Thomas Mark Harmon is an American actor. He is known for playing the lead role of Leroy Jethro Gibbs in NCIS. He also appeared in a wide variety of roles since the early 1970s. After spending the majority of the 1990s as a character actor, he played Secret Service special agent Simon Donovan in a four-episode story arc in The West Wing in 2002, receiving an Emmy Award nomination for the role.
Mark Harmon is affiliated with the following schools: