Shoot to stop
I'm not worried about the legal ramifications of self-defense. I figure you'll probably be sued by the bad guys family whether you were justified or not.
I believe if the situation is desperate enought to require gunfire we should not "shoot to kill" or "shoot to wound". The reasons for this are quite simple. First, it is not our function to serve as judge, jury, and executioner. Therefore, we should not be placed in the position of making a conscious, deliberate decision to kill anyone. At the same time, it is negligent in the extreme to attempt any sort of "shooting to wound" under combat conditions. Remember we only shoot as a last resort to halt a lethal atack, and this highly charged situation will be complicated by stress, possible injuries or fatigue from a fight, by poor light or bad weather, and by other factors. under these conditions, NO ONE is good enough to shoot for the extremities or so-called non-vital areas. To attempt such a shot under these conditions almost always results in a clean miss, which not only recklessly endangers everyone downrange, it reduces your chances of survival.
Therefore, if forced to shoot at a human being, you should "shoot to stop". The goal is to render the attacker physically incapable of further hostile action as quickly as possible, in order to save your life or that of an innocent person. Whether the attacker recovers from his wounds or dies is not the question of the moment; the sole over-riding concern is that he immediately STOP what he is doing. For this reason, any shot fired at a human being should be directed with the intention of striking a vital area, with the intention of disrupting vital bodily functions and quickly rendering the attacker incapable of pressing his attack further. Shoot no more than necessary to stop the attacker's aggressive actions, but continue to fire until he is no longer able to effectively fight back, continuing to endanger your life or that of others.
Just my .02,
wahuwa