Murder vs. Killing

Matt of Left in the West posed an interesting philosophical question that quickly became hijacked. The question is: Are all killings murder?
Suppose for a moment, that someone says that they are coming to kill me, and they arrive at my door with a rifle, and shoot and miss me. If I fire back and kill them, is that murder? Obviously no, since it would be in self defense. But what if they haven't shot yet? If I still suffer from apprehension, is that not still self defense?
What if they say they are going to kill me, and I think that they have a weapon, but they take no active steps in the furtherance thereof, and I see them on the street and shoot them because they said they were going to kill me. Ah, there's the rub.
Another question, suppose that police officers have received a report of a child abduction and are in hot pursuit. The offender runs a red light, with the officers directly behind them, who, unfortunately, collide with a minivan, killing the mother and three children inside. Is that murder?
Part of the problem stems from the misinterpretation of the biblical prohibition of thou shall not kill. This is incorrect, since it really says thou shall not commit murder. There were plenty of situations where killing was authorized, homosexuality, adultery, sassing your parents, just to name a few, so that killing was okay, in response to another wrong. (Okay, I am not justifying this sort of action, merely reporting.)
This leads into the hijacking of Matt's thread. If you are a soldier in Iraq, and receiving fire from a building, and you fire back and accidently strike an innocent bystander, is that murder? I think not, since it is much like the police chase above. Murder requires the deliberate intention to unjustifiably kill. Accidental deaths are no less traumatic for the victims and their families, but it is a different motive from intentionally killing innocents for the soldier.
Many of the comments seem to focus on the thought that we in the US do not consider it murder if people of a darker skin color are killed. This sems to be a veiled implication that we are racist. I think that the evidence would go the other way. For instance, the failed operation in Somalia began as a humanitarian mission and changed when the Somalis who were trained by Al Quaeda began attacking UN troops.
As I have said before, we tend to overlook murder by people of another skin color, so long as they are only killing people of the same color. Think Rwanda, Darfur for example.
I knew a pacifist once, who said that if someone was going to kill her and her family, her belief required her to not resist, thereby showing the moral courage of her actions (or lack of actions). This is fine, so long as the killers have any sort of conscience. But if they don't, what good does dying really do?
Is it murder to protect yourself? I do not think so, and rely on the old dictum, that the right to self defense is never denied.
Oh well, drifting here, so I need to go to work.