Emergency services have descended on Castle Meadow on what is expected to be one of the busiest nights of the year for police.
The incident is said to have occurred at around 6.20pm.
Tom, 26, from Horsford said: “There was shouting that someone got stabbed.
“He got off a bus covered in blood.”
Norfolk Constabulary and the East of England Ambulance Service have been contacted for comment.
More to follow.