Neighbours phoned 999 after a man reported that his son had died at their flat in King's Lynn.
Emergency services were called to the property in Browning Place, in North Lynn, at about 3.45pm yesterday.
A spokesman for the East of England ambulance service said they sent a road ambulance, officers and a doctor from the Norfolk Accident Rescue Service.
The East Anglian Air Ambulance arrived at around 3.45pm, but the man was pronounced dead at the scene.
The area around Browning Place was cordoned off by police while an investigation was carried out.
Neighbours said today that a man came to their flat yesterday afternoon.
One woman, who did not wish to be named, said: 'A father and son lived at the flat. I think they may have been Portuguese.
'The father came to our flat in a very distressed state and told us that his son had died. We called the emergency services.'
A spokesman for Norfolk police said the death was not being treated as suspicious.
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