From Wikipedia, the free encyclopedia. Michael O'Neill (born May 29, 1951) is an American actor. With a career stretching through three decades, he usually portrays senior law enforcement or military officers. He is perhaps best known for his role as Special agent Ron Butterfield, the head of President Josiah Bartlet's Secret Service detail, on The West Wing. He played CTU Administrative Director Richard Walsh in the first two episodes of 24. He played Sgt. Maj. Ron Cheals in the CBS action-drama series The Unit. He starred in the Season Six 2 part Finale of Grey's Anatomy as the broken widower who holds the hospital hostage with a 9mm while pursuing the doctors responsible for unplugging his wife. His most notable film performances occur in Seabiscuit, Secondhand Lions, Transformers, Dancer, Texas Pop 81, Traffic, Sea of Love, A Quiet Little Marriage, Nothing But the Truth, and Green Zone. O'Neill graduated from Auburn University in 1974. After attending Auburn he spent time under the tutelage of actor Will Geer and his daughter, Ellen, at Theatricum Botanicum in Los Angeles before moving to New York to pursue his career there.
Transformers
(Tom Banacheck)
Green Zone
(Colonel Bethel)
Dreamcatcher
(General Matheson)
The Gun in Betty Lou's Handbag
(Jergens)
Air
(Joe Dean)
Around the Bend
(Cowboy)
Blind Justice
(Spencer Heymen)
A Quiet Little Marriage
(Bruce)
Dancer, Texas Pop. 81
(Mr. Lusk)
War of the Worlds
Dallas Buyers Club
(Richard Barkley)
For Their Own Good
(Clark Thompson)
An Unremarkable Life
(Michael)
Bride Hard
Bushwhacked
(Jon Jordan)
The Grim Sleeper
(Detective Simms)
Virtual Obsession
The Legend of Bagger Vance
(O.B. Keeler)
Traffic
(Lawyer Rodman)
Nothing But the Truth
(CIA Director)
ATF
(Asst. A.T.F. Director Ben Walker)
Crazy
(Ralph Christianson)
Victim of Love: The Shannon Mohr Story
(Dick Britton)
Secondhand Lions
(Ralph)
Indivisible
(Chaplain Rogers)
The Sunchaser
(Agent Moreland)
Jennifer Eight
(Serato)
Danger One
(Beckwith)
Ghost Story
(Churchill)
Sea of Love
(Raymond Brown)
Clemency
(Chaplain David Kendricks)
Lorenzo's Oil
(School Psychologist)
Beyond Betrayal
(Ray Pasquerello)
The Stand at Paxton County
(Dell Connelly)
J. Edgar
(Senator McKellar)
American Crime
(Sheriff Smyth)
Seabiscuit
(Mr. Pollard)
The Mod Squad
(Greene)
Cold Call
(Christian)
Awake to Danger
(Detective Brickman)
This Is Us
(Arlo)
JAG
(Commander Bradley)
The X-Files
(Patrol Captain Van Gelder)
Roswell
(Philip Evans)
Chicago Hope
Ghost Whisperer
(Nolan)
The Glades
(Trent Staley)
Rizzoli & Isles
(Jonathan McKnight)
24
(Richard Welsh)
24
(Richard Walsh)
Extant
(Alan Sparks)
FlashForward
(CIA Director Keller)
Law & Order: LA
(Jeb Monroe)
Diagnosis: Murder
(Sheriff Buck O'Hara)
Bates Motel
(Nick Ford)
Manhattan
(Psychiatrist)
The West Wing
(Ron Butterfield)
Sons of Anarchy
(Anthony Franklin)
The Mentalist
(Sheriff Nelson)
Grey's Anatomy
(Gary Clark)
11.22.63
(Arliss Price)
One West Waikiki
The Nine
(Pete Burton)
Echoes
(Victor McCleary)
Rectify
(Senator Roland Foulkes)
Fringe
(Sheriff Velchik)
Scandal
(Lonnie Mencken)
The Resident
(Joshua Williams)
Prison Break
(Herb Stanton)
NCIS: Los Angeles
(Ret. U.S. Army General Richard Collins)
NCIS
(Riley McCallister)
ER
(Col. Ken Kilner)
Commander in Chief
(Congressman Wilcox)
The Unit
(Ron Cheals)
Shooter
(Ray Brooks)
Tom Clancy's Jack Ryan
(Senator Mitchell Chapin)
Criminal Minds
(Det. Yarbough)
Fire Country
(Harlan Denbo)
Outer Range
(Judge Pettigrew)
Leverage
(Judge Roy)
The Romanoffs
(Ron Hopkins)
Without a Trace
(Thomas Shannon)
The Shining
(Daniel Edwards (uncredited))
S.W.A.T.
(Carl Luca)
Crossing Jordan
(Chris Benz)
Messiah
(Cameron Collier)
LAX
(Alonso Mathews)
Happy's Place
(Jim Jackoway)
Millennium
(County Prosecutor Calvin Smith)