COLLEGE PARK, Md.—Federal prosecutors in Maryland are seeking a 35-year prison sentence for a gang member who pleaded guilty to participating in the killing of a 16-year-old boy who was stabbed and cut more than 100 times before his body was set on fire. A judge is scheduled to sentence Kevin Alexis Rodriguez-Flores on July 19. He pleaded guilty in April to conspiracy to participate in a racketeering enterprise and conspiracy to destroy and conceal evidence. Rodriguez admitted that he was a member of Mara Salvatrucha street gang, or MS-13 for short, and took part in the March 2019 killing over the mistaken belief that the boy, a fellow member, was working with police, prosecutors said in a court filing on Friday. The boy was beaten and stabbed or cut roughly 144 times by Rodriguez and others whom he believed to be his friends, they wrote. The killing took place …