His television and motion picture roles have included Chesty Puller in The Pacific, Luther Sloan in Star Trek: Deep Space Nine, Sheriff Jim Valenti in Roswell, convict Heywood in The Shawshank Redemption, Senator Vernon Trent in Hard to Kill, Death in Bill & Ted's Bogus Journey and Bill & Ted Face the Music,[2] and Colonel Stuart in Die Hard 2.

After graduating from high school, he enrolled at SUNY Geneseo; then spent two years at Cornell University, where he earned his master's degree in acting with a minor in speech communications.

[citation needed] A chance meeting with an old schoolmate on a trip into the city resulted in Sadler's casting in an off-off-Broadway production of Chekhov's Ivanov.

After a brief turn at the Trinity Square Repertory Company in Providence, Rhode Island, Sadler moved back to New York and rented an apartment in the East Village, beginning twelve years in which he appeared in over 75 productions, including originating the role of Sgt.

Sadler is best known for his roles in the 1990 action film Die Hard 2 as Colonel Stuart, as Heywood in the 1994 prison drama The Shawshank Redemption, Death in the 1991 comedy Bill & Ted's Bogus Journey, and as Brayker in Demon Knight.

His other film credits include Trespass, K-9, Project X, Disturbing Behavior, Kinsey, The Battle of Shaker Heights, Purple Heart, Jimmy and Judy and August Rush.

Sadler's TV guest appearances include In the Heat of the Night, Roseanne, Tru Calling, Tour of Duty, CSI, Numb3rs, and Law & Order: Criminal Intent.