Michael O'Neill is an American actor who played Secret Service Agent Ron Butterfield on The West Wing. The veteran character actor has appeared in a number of motion pictures, including Dreamcatcher, Seabiscuit, Secondhand Lions (with Eric Balfour), Transformers (with Glenn Morshower, Chris Ellis and Madison Mason), Green Zone (with Jason Isaacs), J. Edgar (with Geoff Pierson, Ken Howard, Stephen Root and David Clennon) and Dallas Buyers Club. He's also had recurring roles on a number of television programs, including 24, Vegas, NCIS (starring Mark Harmon and Rocky Carroll), Grey's Anatomy, Prison Break (starring William Fichtner and Robert Knepper), The Nine (starring John Billingsley), and Commander in Chief (starring Anthony Azizi).