At the weapons training courses for self-defense, they tell you to aim first for the torso, not the head. They say a chest shot will bring your attacker DOWN promptly. Then, you can deliver the coups de grace to his noggin at your leisure. I don't know. I'm just going to fire at him, and keep firing, until my gun is empty.
Although, I just noticed that in this case the victim appears to have been handcuffed, so whoever did him in was shooting fish in a barrel. That's not self-defense.