 "Shooter" depicts a number of sniper tactics, thanks to the guidance of former U.S. Marine scout sniper Patrick Garrity, who trained Mark Wahlberg for the film.Garrity taught Wahlberg to shoot both left- and right-handed (the actor is left-handed), as he had to switch shooting posture throughout the movie, due to Swagger's sustained injuries.He was also trained to adjust a weapon's scope, judge effects of wind on a shot, do rapid bolt manipulation, and develop special breathing skills.