Like a swarm of bees, the message was rapidly relayed, and soon, there wasn't a single undead who did not know precisely the distance and position of their enemy, from the angle the arrows had taken, it was easy to tell that not only were they shot from a great distance that would leave most archers to shame as this particular one seemed to maintain their accuracy even from there, but it was also shot from beyond a dune that should be obstructing vision, meaning that the shots were perfectly curved over it and that the archer was doing so without a direct line of sight.
As far as ambush sharpshooting went, the living attacking them was acing it, few would be able to see anything coming, few would manage to find out where the shooter might be hidden and even fewer would be able to do it as quickly as the undead had.