First of all, knowing the area and that particular congregation well, these are overwhelmingly just ordinary, mainstream Jews who you wouldn't particularly recognise if you saw them in the street or even at games. They dress like you or I would. The more religious Jews, in places like Broughton, are definitely very distinguishable by their overt appearance but apart from the Rabbi (and even he's relatively 'modern') they don't use this synagogue.
Second, bullets ricochet or can pass through the initial target (although they'll slow down usually if they do unless they're high velocity and the target is close). I think the police use the H&K MP5, which is lethal up to 200m. The range yesterday was probably less than 15m so the chances are the bullet will pass through the target, or be deflected off a bone. I'd guess that caused the injury to a third-party.