When the beast charges it does so with unequaled swiftness and ferocity. There is nothing else in nature that even comes close. Propelled by limbs that move so fast that muscle and bone are transformed into something more like the afterburn of a jet engine or the tail of a comet, and armed with a lance that glistens like a scalpel under the lights, the creature will not give you a second chance to be lucky.
You can't think about it--the human brain doesn't work work that fast. You can't react--you don't have that luxury. Life and death are separated by micro-seconds. You have to anticipate. You must call upon the cunning bred into you by ancestors who beat the one-in-a-million odds against survival. You must employ the kill-for-sport mechanism that exists in you on a cellular level, the blood-lust that has enabled your species to infest the planet like liver flukes overrunning a once-healthy organ.
To bring down the mindless brute you must rely on coincidence. Flesh and bone and blood must collide with metallic projectile in a fatal coincidence that defies mathematical probability. It is luck and luck alone that allows you to bag a charging hummingbird.