Honestly, if he really was someone that survived for 100 years he wouldn't hesitate and kill that guy right now and try to absorb his ability if that doesn't work making sure he stays dead for good and his corpse destroyed would also by a wise choice, because this trash may very well be the one stupid enough to die under some zombie get eaten, absorbed and with that create the Undead king.
Someone that knew of that risk, would let him never ever run free.