PHILADELPHIA (AP) — Authorities say a woman was shot and killed when she answered the door of her Philadelphia home. But it’s not yet known what sparked Thursday night’s shooting. Police responding to reports of shots fired found the 22-year-old lying on the living room floor by the front door. They say she was shot at least once in the chest by a man who fled the scene on foot. Authorities say the woman’s 4-year-old son and other family members were also in the home at the time but were not injured.