The game may not follow the ghost's actions in that much detail, especially since I don't recall anyone reporting that they actually saw the ghost doing any killing. It may just start a timer if you release the ghost and leave the area. If he is not re-sealed in the stone within 5 minutes (for example) the traders looking for the urn die, after 10 minutes the elves by the talking tree are gone, and after 15 minutes the elves in the village start to die. I never played with this, and do not know the actual time limits.
