Look up "Southnarc" - the screen-name for Craig Douglas. Read through his background, and understand why you (and we all) should heed his advice.
One of his pet-peeves?
The stationary vehicle. Ignition off. https://homeguntraining.files.wordpress ... ntacts.pdf
That your ignition was on was a good - great - thing. Remember that any deadly-force will have its consequences. I'd much rather just back the car out of there (or, even better, just to throw it in drive and gotten out of there, having backed into the space and "nosed out" the vehicle) and get away. Remove yourself and your loved ones from the threat. And remember, under the law, we are required to do so, if at all possible. (And besides that - let's say that you've got a gun and the aggressor has a gun, too. Great, you guys exchange fire. How well does that play out for your children in the back?
That screen/call is temping to every single one of us. Task-fixation is very problematic, and is something that I am always trying not to run afoul of, myself. Even if you had a gun at the time, remember that you're coming from the defensive: you are re
acting to the action of the aggressor. You're always going to be on the lower part of the power curve. Locking your vehicle doors and making sure the windows are up are definitely very smart things you've done, and are practices you should continue.
Having a gun - a good defensive tool - is only one component of the equation.
Much more than having access to this tool and knowing how to use it (there are many considerations for accessing a defensive firearm while seated [and potentially belted] in your vehicle, and even more in terms of the safe discharge and effective use of that firearm in those confines) is having that defensive mindset, and a large part of that is having good situational awareness, particularly in public/"transitional" spaces.