That is really creepy. Do they have an explanation for it?
Nope. Not that I remember. When I was in elementary school, probably around 1996 I rented out a book about paranormal stuff: aliens, ghosts, zombies, you name it.
http://www.virtuescience.com/chupacabra.jpg
Anyways, the book scared the hell out of me. Which lead to me renewing it a few more times. I remember pretty clearly most of the details from it, and nowhere did it say why that thing came up.
They just called it the "phantom at the altar."