Perhaps St. Peter doesn't "punch your ticket" until you arrive at the gate? Suppose ghosts are souls that hang around because they have something left undone before they finish their journey? Who can say...
If it is, as some insist, "demonic possession" what would be the point of that? In the instance reported the only thing changed were questions answered for the family with no particular harm done to anyone involved.
Regards,
GtG
I so should not have gotten involved in this thread. And I knew better.