Born in Hamar, Norway. Parents owned and operated a ski resort high in central Norway. Began skiing at an early age; soon added hunting and shooting, to become an accomplished biathlete. Attempted and failed to win entry to Norway's Olympic Biathlon Team in 1988 and 1992, missing by fractions of a point each time. Joined Beredskapstroppen in 1990, after sister travelling in the Middle East was wounded in a terrorist attack.
Petersen is a nearly unstoppable sniper if allowed the proper setup time. He projects an air of icy calm at all times, prompting teammates to devise various pranks and embarrassing situations to disturb that calm. All attempts so far have failed. While aloof, his unerring accuracy has endeared him to the rest of the team. When not on duty, Petersen often embarks on lengthy solo cross-country skiing trips, disappearing into dense terrain for days at a time.
