Business owners on Magdalen Street and in the St Saviours box park, which only opened last month, found out the grim news when they turned up for work on Friday morning.
Blood remained on the pavement under the flyover in an area cordoned off by police for most of the day – and detectives are yet to find the person stabbed.
A nearby phone box, which appeared to have blood on its floor, also had a cordon around it.
Bloody debris could be seen behind the cordon (Image: Jack Warren)
The incident happened at 6.30pm on Thursday and a police spokesman said a man aged in his late teens and a teenage girl were both arrested on suspicion of grievous bodily harm with intent.
They were taken to Wymondham Police Investigation Centre for questioning.
Although saddened by the stabbing, workers at the box park and on Magdalen Street say they are not surprised because the area is known for anti-social behaviour.
Police were at the scene all night (Image: Jack Warren)
Greg McCleod, 45, who works in a nearby shop, said: “It is Magdalen Street, things like this happen.”
Another local who wished to remain anonymous said: “It is the usual for Magdalen Street.
“The phone box is a notorious place where people order drugs.
The phone box was also cordoned off (Image: Jack Warren)
“I watch drunk people there all the time and the police do nothing sadly.”
Leroy Barrett, 53, from Mercury Communications, a shop in Magdalen Street, said: “You read about stabbings all the time and I think we are immune to them but at half past six it is a little troublesome.
“The area has a bad reputation and to be fair it is undeserved. There are not a lot of issues around here.
Leroy Barrett who works on Magdalen Street (Image: Jack Warren)
“You cannot escape knife crime.”
Another man who works nearby added: “It is not that shocking for Magdalen Street.
“It is awful, but not really a shock.”
Gemma Corson, 32, who works at Wizards Flame in the box park said: “You would have thought people would have seen it happen.
Gemma Corson who works in the box park (Image: Jack Warren)
“It is really sad. The sad thing is, it is not shocking. I would expect it to happen here.”
Jenny Wright, 68, who works at Piecework in the box park, said: “The underpass has always been rough.
“I think this development is really going to help.
Jenny Wright (Image: Jack Warren)
“When I was a girl Magdalen Street was quite posh.
“I have always felt safe in Norwich. It is about who you are with rather than where you are.”
David Jonson, 61 added: “I came down this morning and it was all blocked off.
“It is very strange and pretty shocking.
David Jonson who lives locally (Image: Jack Warren)
“I think it is a dangerous place down here. People sit here drinking all night.”