Quoted:
a few things, one, everyone will react diff.––both on the internet and in real life
first off, i would descretely draw and keep my firearm in a covert carry method by the time he started walking towards me; if not possible, my hand would already be descretely positioned for a draw
where are his hands?
2nd, i would not shoot or present a weapon UNTIL there is a presence of some intention, ability, and opportunity of him using deadly force/having harmful intent...so far, in your senario, you have a retard, who may be deaf, that has no weapons present, no threating motions or verbal (threat) intentions walking in your direction––hell, you really cant justify that he IS heading towards you (for all you know, after you told him you dont have the time, he might just be walking past you to the gas station/etc)
retreating in a cautious (gun at covert ready) and decisive and aggressive way would be my goal––put the car, the pump, car door, etc physically between me and his path, but still keep my eyes on him and his hands....it doesnt matter if the state you are in, or if you "have no duty to retreat"
there is nothing wrong with retreating in this situation (yet)––no need to escalate a situation that may be nothing, no reason to show your hand before otherwise
you can "stand your ground" if you want, but its stupid to do so if you can walk/drive away; some things are worth killing/going to prison for...DRTing some dude on a stroll at a gas station looking for the time probably isnt one of em
that said, if the BG is already the distance to your vehicle and making no intentions of going anywhere but towards you...full verbal challenges (STOP!)
where are his hands? where is your gun?
if he makes a CLEAR intention of bodily harm towards you, such as closing withing the premese of your vehicle (hands in pocket or weapons in hand, etc) and does not respond to the verbal challenges...FIGHT and DRT
PS: mace/non-lethal methods might be a better call to have in your other hand if he still does not have any weapons, present any other intentions, etc, but still is walking within your personal space
YMMV
Don't tunnel vision though, threat scan for his buddies. If they are around it may very well be go time.