She kept helping Caitlyn work to clear the hole. It was going to take the two of them a little while to get through it all, so it gave her a moment to think about the question. It was a fair one, but one that likely didn't have a great answer.

As she started to collect the bones, she frowned down at them and sighed.

Ghosts do crazy things because they're usually pretty insane.
I would imagine it was probably betrayed or killed by a sleeper so it wants vengeance.
But the one it wants it on is long gone now, probably.