Adept at playing disturbed, disheveled individuals, this native Chicagoan honed his acting skills on stage before relocating to Hollywood in pursuit of TV work. Although he landed a number of guest spots, as well as a recurring role as an alcoholic cop on the 1960s-set drama American Dreams, it was his turn as a vengeful rapist on Crossing Jordan that changed his career. While working on the episode, he impressed executive producer Dennis Hammer and series creator Tim Kring. When the two went on to work on the sci-fi smash Heroes, they cast him as an emotionally unstable, radioactive madman. Although his character was killed off before the end of the show's first season, Armstrong has continued to work on the small screen as an in-demand character actor, with appearances on Private Practice, The Mentalist and CSI: Miami. Off-screen, he is married to his former Heroes costar, Ashley Crow.
- Secured a two-year John Belushi Memorial Scholarship to attend the College of DuPage in Illinois, where the late comedian also studied.
- Before breaking into television, Armstrong appeared on the Chicago stage in a Shakespeare Repertory Theatre production of Hamlet and the Steppenwolf Theatre Company's 1998 revival of The Man Who Came to Dinner, which costarred Frasier's John Mahoney.
- Made his TV debut in 1999 on the short-lived CBS cop drama Turks, a role he secured in part by falsely claiming he was an extra in two Julia Roberts movies filmed in Chicago.
- Due to his hirsute look on Heroes, many fans mistakenly came to believe that he also played the caveman in the Geico commercials.
- Ashley Crow — Wife
- College of DuPage, Glen Ellyn, Illinois, United States
- Birth Place: Chicago, Illinois, United States
- Profession: Actor