Witnesses have described the "horrendous" moment two cars ploughed into crowds at a "car cruise" event in Stevenage.
At least 17 people have been injured, some seriously, after the incident last night (July 18) at the "Cruise Herts" meet.
Spectators claimed at least one of the vehicles involved, a Nissan 350Z and a Toyota GT86, was travelling at up to 70mph in the moments before the crash on Monkswood Way.
Organiser Rix Sidhu said it was the first time the Cruise-Herts group had suffered any serious incident in its 17-year history, with static meets often held in closed-off spaces where enthusiasts show off their modified vehicles.
Mr Sidhu said a small number of cars "went rogue" and left the car park, where crowds lined the main road to capture footage of the vehicles at speed.
Mr Sidhu said the meet was being help in aid of the 4Louis charity, an organisation which supports those affected by miscarriage, stillbirth and the death of a baby or child.
He said organisers were first-aid trained, and that a liaison officer worked with police to pass on the registration plates of anyone causing trouble.
"Nobody wanted this," he said. "We try so hard to make sure this doesn't happen, we beg people not to race on the roads, if they want to race, there are places they can go for that, tracks where they can go at speed."
He said organisers had taken the decision to cancel all further meets.
He said: "Some people like drinking and that sort of thing, we just like cars. They are our pride and joy, what we are interested in.
"Unfortunately this incident means we are all going to be tarred with the same brush - people will say we are boy racers.
"But we've decided we're not going to run these any more.
"After 17 years, it's over."
The East of England Ambulance Service said it had taken 12 people to three hospitals, Lister Hospital in Stevenage, Watford General Hospital and The Princess Alexandra Hospital in Harlow.
An air ambulance also attended the incident.
Assistant Chief Constable Nathan Briant, from Hertfordshire Police, said they had "identified the drivers of both cars involved in the collision and they have been interviewed".