[1]: 344 Petersen came back to live in the United States in 1991 and started studies for his BA degree in Economics at St. Olaf College in Northfield, Minnesota.
[1]: 344 Petersen and Darrell Hardy wrote the Nocturnum adventure trilogy for Call of Cthulhu: Long Shades (1997), Hollow Winds (1998) and Deep Secrets (1999).
[1]: 345 Petersen and Kevin Wilson designed the Game of Thrones (2003) wargame, and Doom: The Boardgame (2004).
[2] In addition to his responsibilities as CEO, Petersen managed the day-to-day operations of Fantasy Flight's development and design department.
On July 30, 2018, it was announced that Petersen would be stepping down from his role as CEO of Asmodee North America at the end of 2018.