Unfortunately, Virginia is one of the VERY FEW states that has NO statues on the use of deadly force. Each and every shooting case is assesed individually, and many (most) of them are decided by a jury in court. Killing someone here is automatically homicide (second degree). It is a positive defense that you did it in "self-defense" (which can extend to others) but that justification can only come later. To prove second degree murder, the Prosecutor only has to prove that you killed him. It's up to you to prove what the justification was. By using "self-defense" you have to admit to the charge in the first place.
This sounds worse than it really is. Generally speaking it's reason and common sense, but there is no law that says when you can or cannot shoot as most other states have. It's for a jury, DA, judge, whatever to decide if you were reasonable in your actions.
Case law does state that you may respond with the same level of force that is being used against you.
-A person who reasonably apprehends bodily harm by another is privileged to exercise resonable force to repel the assault. However the amount of force used to defend oneself must not be excessive and must be reasonable in realtion to the preceived threat (Diffendel v. Commonwealth, 1989)
The "brandishing a firearm" law does not apply in cases where the firearm is being used legally in self-defense. See state statute 18.2-282.
Pulling a gun is however the "threat of deadly force". Even reaching for one may be construed as such. Basically the threat for deadly force is judged the same as the acutal use of deadly force. As there are NO legal statues concerning when you can, and when you can't. You're basically in the same boat in either circumstance. Either action (situation #1-pulling the gun, or situation #2-shooting) is going to have to be justified to the courts.
There isn't a cut and dried escalation of force you need to go through in VA. You don't need to issue verbal warnings, etc or even retreat under certain circumstances. If the "threat of deadly force" is enough to stop the incident, then you'd be wiser to not shoot. However you must realize that the "threat" and the actual "use" of deadly force are basically the same. Once you've pulled that gun, you've made the concious decision that the only resort you have is to use deadly force to control the situation.
Obviously you're going to be better off if you don't kill, and issuing a warning, etc may be the way to go. But that's pretty much your call that you're going to have to justify afterwards. If you didn't think the guy was going to really kill the clerk, you were playing vigilante, or for some other reason you weren't justified in killing him (few that may be), you may not be justified in the threat of deadly force.
As for being charged with "brandishing" it does not apply to justifiable self-defense, so you're going to have to justify it before the courts (as would be expected in VA).
Ross