Peter Killian Gallagher (born August 19, 1955) is an American actor, musician and writer. Since 1980, Gallagher has played roles in numerous Hollywood films. He starred as Sandy Cohen in the television drama series The O.C. from 2003 to 2007. He currently appears in a recurring role on the USA Network drama Covert Affairs, as CIA Clandestine Services Director Arthur Campbell. Gallagher was born in New York City, New York. His mother, Mary Ann (née O'Shea), was a bacteriologist, and his father, Thomas Francis Gallagher Jr., was an advertising executive. Peter is the youngest of their three children. His brother is Paul Killian Gallagher and his sister is Joan Killian Gallagher. He is of Irish Catholic background and was raised in Armonk, New York where he graduated from Byram Hills High School. Gallagher graduated from Tufts University, where he had been active in theater, appearing in such shows as Stephen Sondheim's Company and singing with the all-male a cappella group the Beelzebub. …