John T. O'Brien

John T. O'Brien. Actor: Chicago Fire. John T. O'Brien is an American actor, writer and musician best known for his roles on the TV series Chicago Fire (NBC), No Apologies (Fox) and In An Instant (ABC). He wrote, executive produced and starred in Dad Man Walking, an original pilot for television directed by Clare Cooney. He was born in Chicago where he studied acting and improvisation.