A dad-of two was allegedly stabbed to death in front of his son during a reported row between neighbours over noisy motorbikes.
The victim, who is said to have been knifed in front of his teenage son, was named locally as Dean Allsop, aged in his 30s.
Locals said that Mr Allsop and his son had been trying out their trial motorbikes when a neighbour objected to the noise and went out to complain.
An argument started which led to the mass stabbing with Mr Allsop dead and three other people taken to hospital with knife wounds.
Police confirmed that two men had been arrested at the scene beside an area of communal garages in Primrose Crescent in Thorpe St Andrew near Norwich, Norfolk.
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Norfolk Police said emergency services were called to Primrose Crescent shortly after 7.35pm on Wednesday "following reports of a disturbance involving a number of people".
It was confirmed that armed police were among officers who responded.
Paramedics battled to save Mr Allsop but he was declared dead at the scene, close to his semi-detached home where he lived with partner and two sons.
His friend Aaron Barkshire, 29, who lives nearby, said: "Dean and his son who was aged 17 or 18 both had road legal motorbikes and were going out for a ride.
"This neighbour went outside because he didn't like the noise of the bikes. There was a bit of a verbal argument and it just turned nasty.
"Dean and his son were with the bike and he didn't like the noise, so he came out giving it a lot. Dean rang the police and it got a bit verbal between them.
"It is awful that something so trivial caused this. It is just phenomenal."
Mr Barkshire, who is a motorcycle mechanic, said he witnessed the start of the argument and walked away to his garage.
He said: "I didn't want to get involved being a neighbour of both parties. I went into the garage and that is when I heard a knife was involved so I locked myself in my garage.
"I was fearing for my life because there was a guy with a knife and I thought I would be next, but I didn't hear any commotion or anything.
"My Mrs rang me to ask me if I was OK because she could hear what was going on.
"I decided to go back to my house and as I went out, Dean's son was shouting to me to call the police because his Dad had been stabbed multiple times.
"I saw this guy standing there with a knife. It was a big knife. I was fearing for my life because this guy had seen me go into the garage and there was a massive knife. I thought I was next in the firing line.
"I saw Dean covered in blood, but he was alive at this point. We heard a lot of commotion and I think it carried on thereafter. It was all in a blue like slow motion."
Mr Barkshire described Mr Allsop as having "a heart of gold".
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He added: "He treated my kids as one of his own."
At least eight police cars, ambulances and rapid response vehicles were seen in the area after the stabbing.
An East Anglian Air Ambulance helicopter was also called to the scene and landed on nearby playing fields.
Retired health care assistant Eve Cooper, 67, said: "I realised something was happened when heard the ambulance and saw the police cars.
"Then the helicopter came down so low that I could see the pilot. It was pretty awful. I am a Londoner and I felt safe here, and I want to feel safe again."
A Norfolk Police statement said: "Officers arrived on scene to find four people with injuries. Despite treatment by paramedics, a man was pronounced dead at the scene.
"Three other people were taken to hospital for treatment to suspected knife wound injuries.
"Police arrested two men at the scene in connection with the incident who will be questioned in due course.
"Police have cordoned off the scene in Primrose Crescent while enquiries are carried out."
Superintendent Tracey Little of Norfolk Police added: "A number of police resources, including armed units, were deployed to the scene.
"A murder investigation has been launched and we are in the early stages of our enquiries to establish the circumstances surrounding the incident.
"We would like to hear from anyone who may witnessed the incident or has information concerning it."
Police forensic teams were still at the scene on Thursday and the area remained cordoned off by officers.
A tent which was believed to be covering potential evidence was visible outside the communal garages area.
Thorpe St Andrew is a small town and suburb east of Norwich and has a population of around 15,000 people.
Police are appealing for anyone with information to call 101.