..... It's all about whether or not a reasonable person in the same situation would have acted as he did.
Maybe I'm just being too nit picky....or woke up on the wrong side of the bed this morning....
The part in blue is very relevant. If the actor had the opportunity to run away but did not, they should be able to articulate why they believed this would have not stopped the "attack". If the actor had the opportunity to punch the attacker in the head but did not, they should be able to articulate why they believed this would have not stopped the "attack". This goes on....
If the only justification for using a firearm is that they happened to possess one at the time of the confrontation then this is no justification at all.
Also, the actor had better be able to articulate exactly what the threat was as they believed it to be.
...So, there's not a: "If person is unarmed, you can use a baseball bat, if they have a baseball bat, you can use a gun" type of thing. It's all about whether or not a reasonable person in the same situation would have acted as he did...
Unless the person is actively physically attacking you or has already attacked you and is coming back to do you further harm, when exactly is it reasonable to shoot an unarmed person? To hit an unarmed person with a baseball bat?
Do you see why I am a proponent of having other use of force options and having the mind set to do so?