Xander Berkeley

Alexander Harper "Xander" Berkeley (born December 16, 1955) is an American actor. He is best known for his television roles as George Mason on "24", Sheriff Thomas McAllister on "The Mentalist", Percy Rose on "Nikita", the Man on "The Booth at the End" and Gregory on "The Walking Dead". 
His movie roles include Christopher Crawford in "Mommie Dearest", Todd Voight in "", Trevor Lyle in "Candyman", Ralph in "Heat", Agent Gibbs in "Air Force One" and Dr. Lamar in "Gattaca".