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. From 2010 to 2014, he played CIA Clandestine Services Director Arthur Campbell the USA Network drama series Covert Affairs.