Police are investigating the death of a five-month-old baby boy in Whangārei as a homicide.
Emergency services were called to an address in the city at 8.30 last night, but the baby had died at the scene.
Police arrested a 28-year-old man at the address and he has been charged with assault on a child. He will appear in Whangārei District Court this morning.
Northland police investigations manager detective inspector Dene Begbie said the investigation remains open and police could not rule out further charges being laid.
"Our deepest sympathies are with the family during this difficult time."
Neighbours told 1 NEWS they were aware something was happening next door when they heard a bang last night.
They looked out of the window and saw two ambulances and a fire truck.
They said the couple there had lived in the house for about a year with their two young children.
They were friendly and appeared very happy, neighbours said.