based on the scenario you present, yes you can use deadly force on the perp..... for VA, the 3 questions that give you the right to use deadly force taught in an NRA handgun safety class for concealed carry .
1. Is your life in jeopardy or someone else's life in jeopardy of bodily harm /imminent danger (i'm about to be robbed, fear for my life)
2. Does the perp have the ability to do harm to you that may result in grave bodily injury/death (seeing the perp has a gun and using it to commit a felony against me that may result in death/injury)
3. Does the perp have the means to do harm to you that may result in grave bodily injury/death (perp has a gun and plans to use it on me)
If yes to all three, then you can use deadly force.
Of course there are repurcussions... possible civil suit, court/attorney fees... whatever you do... only statement that should be made when the police arrive is " i would like to cooperate, but i can't make a statement until i speak to my attorney" Let the police talk to the witnessess if any about what happened. This will help back up your statement when you do give it. This protects you from any statement you give that you may need to recant later. Your adrenalin is still pumping after the shooting that you may miss important pertinent information that may exonerate you .