 Born in Ann Arbor, Michigan, and raised in Farmington Hills, Michigan, Petry spent three years playing varsity hockey at St. Mary's Preparatory, in nearby Orchard Lake Village.He left prior to his senior season in November 2005 to play for the Des Moines Buccaneers of the United States Hockey League (USHL), a member of the team's 2006 Tier 1 National Championship-winning team.Petry was then drafted by the Edmonton Oilers of the NHL in the second round of the 2006 NHL Entry Draft, 45th overall.