@Genstabler:
The significance is the perception by the public, or more likely by the press or politicians. Like it or not, and whatever the objective considerations of risk tell us, this incident will attract added attention because complete bystanders were involved. I think it would have attracted a lot of attention even if all the casualties were spectators who might be deemed to have placed themselves at risk (although when I'm behind the crowd line at a display, I assume that the risk is well-managed and very small). But here, there are factors that will amplify public concern, or at least what the media calls public concern.