 He studied medicine at the University of Colorado at Boulder but was keener on the stage than becoming a doctor.O'Brien switched to civil engineering under his family's guidance, but his heart was still set on becoming an actor.He moved to New York City and was "discovered" by theatrical impresario Charles Frohman who signed O'Brien to a three-year contract and put him in "The Builder of Bridges", which opened on Broadway at the Hudson Theatre on October 26, 1909, after he had appeared on Broadway in "The Rollicking Girl" (1905).