A day before authorities say he decapitated his father and posted a graphic YouTube video calling for the execution of federal employees, Justin Mohn strode into a gun shop in Bucks County, Pennsylvania, and legally purchased the 9mm handgun police say he used to carry out the killing. “There was nothing legally precluding him from purchasing that gun,” Bucks County District Attorney Jennifer Schorn said during a Friday news conference. In the days before visiting Johnston’s Sporting Goods in Croydon, Mohn, 32, who was unemployed and lived with his parents, had surrendered his medical marijuan…
