On the face of it, it sounds like the organisers just didn't provide the necessary staff to ensure this event passed off safely. Trying to do it on the cheap and max out their profits, no doubt.
What idiots.
I often think we are over the top with our Health and Safety legislation in the UK - x number of marshalls for events, x number of security guards, x arrangements for car-parking etc. or the event doesn't happen - but it's at times like this when I realise that actually it serves a good purpose.
I hope you guys sue, frankly.