Boy, 12, is charged with manslaughter in his nine-year-old sister's shooting death 'after he handed loaded gun to their cousin, five, who pulled the trigger' while they were home alone Nyssa Davis, nine, was shot in the head and killed by her five-year-old cousin in Philadelphia on January 20 Nyssa's 12-year-old brother arrested and charged as a juvenile with involuntary manslaughter and recklessly endangering another person Boy is suspected of handing his young cousin the gun while the children were home without adult supervision Nyssa's father, Blake Davis, 39, charged with involuntary manslaughter, endangering the welfare of children, corruption of minors, gun violations