The people didn't start trying to avoid the sound of gunfire when it started, and before he walked two kilometers?
When you live in a warzone, you get used to intermittent spats of distant gunfire. Would you suggest that they leave the cover of their homes and go running, exposed, through the streets every time it happens? It's better to hunker down, hope you're not a target, and let the walls catch any stray bullets, rather than run about and let your meaty bits catch those rounds. (Around Chicago, in the 1990's, you also called the police, but I'm not sure how effective that step is in southern Afghanistan.)
With regards to the possibility of this event being a CIA hit, someone's going to have to present the significance of the families that were targetted. I don't put it past western intelligence agencies to assassinate people, but I also don't put it past individual soldiers to have an emotional breakdown, resulting in a killing spree. In the case of the former, though, there has to be a reason behind the killing. What were the members of these families doing to warrant being killed?