Two low levels or even a solo low level character with a merc may do this if you are patient.
High levels can solo this without any issues, so it could happen that you spawn the mobs and someone takes them before you have a chance to engage. Just be patient. In two Norrathian hours the quest giver will be back. Don't talk to him if you see others around. If you did talk to him and someone took the mob, the simplest solution is to delete the quest, go back to the tavern, talk to the professor to restart the quest and then go back to the field. This is the only quest that takes a bit of finesse, but usually drops some exquisite loot that's useable at low levels.
This article refers to events, personae and activities only present in-game during the annual Nights of the Dead festivities, which come to Norrath each year from (roughly) mid- to late-October through to early- to mid-November.