If you paralyze Wulfgar while he uses Whirlwind Sprint...

My crossbow has paralysis poison applied to it, which causes the ragdoll effect. The bolt is actually being aimed at where Wulfgar is going to arrive. It’s fired as he starts to duck, so it travels over his shoulder and he actually runs into it, since he’s moving more quickly than the bolt travels. If sniped too early, he will become paralyzed before moving, and if too late, the bolt will hit him after the effects of Whirlwind Sprint have worn off. Shooting Wulfgar does not break the quest. He is essential, and eventually climbs back up the mountain.