SAN DIEGO—Police were asking the public’s help today in an investigation into the shooting death of a 12-year-old boy who was in the backyard of a family gathering on Thanksgiving Day. The shooting happened at 9:34 pm Thursday in the 7400 block of Cahill Drive in the Skyline neighborhood, according to Lt. Jud Campbell of the San Diego Police Department. When officers arrived, San Diego Fire-Rescue Department units were already on the scene and rendering aid to the boy, who had trauma to his upper body, the lieutenant said. “It has been confirmed that, at the time of the incident, the 12-year-old was in the backyard at a family gathering for Thanksgiving,” Campbell said. “He was struck by a single bullet that came from east of his location.” Paramedics took the boy to a hospital, where he died. Police homicide detectives have been investigating the circumstances surrounding the death. “The …