Growing up in the northeast, I was intimately familiar with the terror deer can cause motorists.
From a young age, I knew that drivers had to keep their eyes peeled for any animals that would jump out into the road, and deer were enemy #1. No one wants to accidentally kill an animal, but hitting a deer could also completely total your car. The skittish woodland creatures are totally harmless, but on the road they're basically brick walls.
Even though hitting a deer in a car is dangerous and devastating, imagine having even less protection. When a group of motorcyclists saw their friend completely wipe out, it took them a few seconds to realize just what had hit him.