A cyclist was seen carrying a knife and covered in blood by alarmed residents – before a massive police operation was launched involving the force helicopter.
The man, who was described as holding a “big” knife, is reported as having shouted at pedestrians crossing a cycle bridge on Stourbridge Common.
Police had received reports a fight had broken out near the park earlier on Sunday.
Cambridgeshire police received several 999 calls from terrified residents who spotted a man bloodied and holding a knife as he rode a bike through the city streets.
Paramedics were also needed after a child on a bike was knocked over outside the Green Dragon pub in Water Street near the cycle bridge to the common.
A spokesman for the East of England Ambulance Service said paramedics were called at 6.25pm on Sunday and treated an 8-year-old boy who suffered minor injuries.
Several residents took to Twitter to alert police after spotting the rider.
One tweeter wrote: “We were crossing the bridge and saw a guy holding a knife & shouted at us. My friend called the police.
Blogger Richard Taylor tweeted: “Apparently a rowing crew witnessed the cycling knife-man police are hunting in Cambridge knock over a small child earlier.”
Another tweet said: “I had to ring 999. Someone was walking around with a big knife and blood all over his face.”
:: A 29-year-old man from Cambridge was arrested at 11.50am yesterday on suspicion of criminal damage, affray and possession of an offensive weapon and last night remained in custody at Parkside police station.