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.