Complex sentence: As a child, O’Donnell attended the Fuller School on 41st Street in Chicago however, at age twelve he began his career in show business as an usher at both the Old Chicago Opera House and the now infamous Iroquois Theatre.
Split into simpler sentences: As a child, O’Donnell attended the Fuller School on 41st Street in Chicago. However, at age twelve he began his career in show business as an usher at both the Old Chicago Opera House and the Iroquois Theatre.