This is a 9mm FMJ that has hit and lodged in the spine. Such shots frequently kill or cause immediate paralysis. Don't let anyone tell you a FMJ isn't lethal or effective. Any bullet in this position would be effective. In this case the victim had no long-term effect of this wound which is a medical miracle of sorts.
Nobody can predict the effect of any bullet.
The variables are endless. A .45 ACP that hit bone and that helped expand it. The unknown brand of hollowpoint didn't exit because of the resistance of the bone and expansion that followed. Ideal performance and of course very fatal. These series of skulls with bullet wounds show the vast variance of damage caused by handgun bullets.