There are no sympathetic victims in this mess. Everyone involved made his own contribution, mostly illegal. As a result, whether it was self defense, voluntary manslaughter or murder depends on who did what in the last few seconds before the fatal shot. It's possible for a bad guy, whose previous behavior was provocative, to regain his innocence at the last instant. Andrew Branca goes into this in his book, The Law of Self Defense.
Suppose A walks up to B, shoots him dead, then turns and runs. A is guilty of murder. Suppose one of B's friends goes after A with the apparent intent to shoot him. At this point, A has become the innocent victim of an aggravated assault by the friend. The reason is that the murder of B is over and done with. Shooting A can't save B's life. The purpose of defense is to prevent imminent unlawful harm, not to avenge or punish previous unlawful harm even if it occurred mere seconds ago. If A had continued by trying to shoot C, it would be defense to shoot A in order to save C. To get back to B's friend, it would be self defense for A to shoot him. This may seem convoluted but it makes sense if one thinks of self defense as force used to prevent imminent unlawful harm. The three critical words are "prevent", "imminent" and "unlawful". Unless all three are satisfied, it's not defense.
In my opinion, The Law of Self Defense is essential reading for anyone who would use any kind of defensive force. Gary Young and Chris Zeeb do a good job in the classes they teach but Branca goes far deeper. He has managed to organize statutes and case law governing self defense in a logical way that enables his graduates to avoid breaking the law in the course of defending themselves.
