Much as I agree with the principle of armed self-defense, the reality is that these squeegee men were operating in heavy traffic, at stop lights. Firing a gun at a squeegee man in that setting would be extremely likely to end up hitting an innocent occupant of another car, or a pedestrian.
Seldom in acts of self defense involving firearms is the weapon actually discharged. The mere presence of a firearm held, brandished in response to a threat, or displayed will often be enough, and to do so without valid reason will get you in trouble, too.
There are strict 'rules of engagement', involving the legitimate use or threat of deadly force.
The idea that people at random may be armed will be capitalized upon by those who do not carry, but will buy bumper stickers, etc., to make it appear they are likely to.
That serves as a deterrent to all but the most determined or stupid, and I reiterate, seldom, even then, is it necessary for a shot to be fired.
There is no justification for discharging the firearm (shooting or shooting at someone) without the presence of an immediate threat of serious bodily injury or death (especially in a crowded area where there is potential to harm innocent bystanders).
Displaying a weapon when threatened with serious bodily injury or death, (or acting to prevent serious bodily injury or death of a third party who cannot defend themselves nor retreat), usually deters the would-be criminal from any further pursuit of their goal, and often suffices to take them into custody.
Otherwise, there would be a lot more wounded defendants/suspects in court--or dead ones not.
Virtually every State which has concealed carry widely available has very stringent rules, codified, governing the acceptable use of deadly force in self-defense or the defense of others, and the person with the permit can be held criminally and civilly responsible for everything from displaying their weapon to wounding or killing someone who did not justifiably deserve to be shot on the basis of the incident.
All rights to self defense using lethal force are forfeit if the person 'defending themselves' actually instigated the incident.
The permit is a responsibility, not some sort of 'James Bond license to kill'.
Killing another person, no matter how justified, is serious sh!T, and will change your life--at the very least how you are percieved by yourself and others in your peer group--and is never to be taken lightly.
So kindly do away with any visions of Hollywood Western shoot-outs. That stuff was rare, even in the 'Wild West'.
Firing a gun at a squeegee man in that setting would be extremely likely to end up hitting an innocent occupant of another car, or a pedestrian.
In extremis, angle the shot downward from the car window, which they would be likely standing beside to deliver any credible threat to your person. (Anything less is a property crime, and not legitimate cause for deadly force).
The wound track would be a nasty one, generally aimed from the navel through the pelvis.
Again, at this point, someone would have to be legitimately in fear of their life or serious injury requiring hospitalization, or the shooting would not be justified.
Through and through penetration would be likely to put the bullet into the pavement, with the shot travelling through the lower abdomen and passing within the pelvic girdle or lodging there. Nasty, quite possibly fatal wound.
From an SUV, pickup, or van, the shot angle is easier to get because the window is higher off the pavement.
If you have a carry permit and have not tried to stay ahead of what can happen by playing "What if?", you are only practicing with half of your weaponry at best. The mind is the best weapon you have. It will help you avoid problems, avoid escalation into lethal force situations, and while not foolproof, can go a long way to keep you safe. It cannot do it all though, and having the skill and means to deal with the exceptions can mean the difference between life and death.