[ According to the news article (Korean) from which the picture above came, ] the nails used were construction-grade screws—which ordinary hardware stores do not carry—with the tip sharpened in order to maximize penetration, shot from a modified nailgun (ordinary nailguns can't shoot screws with a thick head). I had thought the culprit could as well be a mentally challenged, but no, this level of preparedness isn't something I would expect from a retard.
The bloody nail shown in the middle picture was surgically removed from the spine of the poor cat in the middle/bottom pictures, which had its lower body paralyzed, was traumatized by the sight of humans, and tried to creep away desperately in fright when it saw the rescue team coming. It died in 2 weeks after surgery.
Human cruelty... *deep sigh*