How To Complete Grave Digger Quest?

In the quest i got access to the graveyard bu the description says to kill saylero's brother but he should already be dead in the graveyard and you cant kill the brother you got drunk, whenever i go into the graveyard i look around but cant find the brother and just get overrun by zombies that 3 shot me so im giving up how do i complete it

(brother should already be dead but it tells me to kill him and brother is not any of the 30 zombies that chases me down in the graveyard)

 

In the cathedral.

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There is a tunnel that goes down behind the priest