I have taken on the skinner mystery in the bridge district. I found both pieces of evidence and got the tanner to admit his guilt. However, he won't die!!! I have done about 3000 damage to him and won't DIE! Can anyone tell me why?

he's supposed to go downstairs and dissapear.
you get to kill him in trademeet after you become "the heroes of trademeet" a lady approaches you and you get the quest finisher.