Opening up with any gun, a pistol or a rifle you have retrieved from a car, is potentially problematic as the police and other bystanders may mistake you for the bad guy. The issue of using a rifle is equally problematic as using a pistol. Even if you call 911 and describe yourself and that you are a good guy, there is no certainty that in the fog of war that the cops arriving on scene will have received that information, been able to remember that information with everything else they are getting, or that there haven't been other 911 calls reporting you as a shooter (and hence the bad guy) by some other observer.
As far as whether impacts to the vest from pistol calibers causing problems for a vested bad guy, it all depends. If you ever get a chance to check the Second Chance documented cases of 'Saves' then you will learn that many of the people shot did not realize they were shot or did not realize they were shot more than once. Some claim to have thought that the shots toward them must have missed, later to realize that they are bruised, have some discomfort, or have damaged clothing and vest. One officer apparently did not realize he had been shot until undressing and the slug fell out and dropped to the floor.
I just love the comments about the guns used. I know there are several reports of guns and calibers for Arroyo and Wilson, Arroyo's apparently not being an AK and contrary to what I have read reported here, one news clip had Wilson's as a .40 Glock.
Duxman, I assure you that it isn't just the antis who misinterpret or misrepresent information. The transgression is blatant on both sides of the gun issue. Some years back, I compared death rates reported by the NRA and MMM. Both cited the same CDC study. Both lied, massaging the data to fit their political perspectives. I was unable to arrive at either total based on the data in the CDC study that both claimed as the basis for their information.