Bonnie, you're not being paranoid. I'm chiming in because I think along a similar path.
In this case, it's my local Safeway. There have been a number of purse-snatchings/knockdowns of women in broad daylight there. In one case, it was a few minutes before I stepped out of the car with my teenaged son. Some poor lady with her 2 daughters had just exited the store when a "kid" ran by her, grabbed her purse, and knocked her down. I was approximately 25 yards from her because I park in the next country to make sure I can see everything around me (not admitting that other drivers would suffer if I had to back out of a space, mind you - lol)
This was a Sunday and from their clothing, it looked like they had just come from church. All I could do was call the cops and give them a brief description of the kid who ran down the hill to what I believe was an awaiting car (freeway entrances there) and try to give her some comfort. I felt bad for the daughters -- freaked out and crying, poor kids. They looked to be about 8 and 5 maybe. The mom didn't want medical, just her husband. Her phone was in her purse, so I gave her mine to call her husband.
We waited together until the husband drove up. What a mess! Not sure how much the Safeway cameras were able to pick up, but you're right -- it's for after the fact