John, who owns a sporting goods store, sells a gun to a boy who is thirteen. On his way home the boy drops the gun on his foot and breaks his big toe. His parents sue John, the owner of the sporting goods store, claiming that his negligence, i.e., his sale of a gun to a minor, caused their son's injury.

Should the boy's parents win their suit against John?

How does Palsgraf apply here, if at all?