PHILADELPHIA — A 14-year-old boy was killed and four other teens wounded in a shooting after a football scrimmage outside Roxborough High School late Tuesday afternoon, police said, marking the 23rd shooting death of a child this year as Philadelphia continues to face a surge in gun violence. Just after 4:40 p.m., Roxborough High junior varsity football players had left the field and were headed to their locker room when four shooters who had been waiting in a car parked outside the field jumped out and shot a volley of bullets toward the group of boys, police said. A 14-year-old was shot in t…