The death of a man in Rangiora, north of Christchurch, on Friday night followed a fight on his driveway with a group of people who turned up uninvited.
Police say the victim's brother tried to resuscitate him without success and he died at the scene. A second man was taken to hospital in a moderate condition after the fight, at a house in White Street.
Detective Inspector Dave Long would not be drawn on whether the brothers knew the visitors or what sort of weapon was used in the fight.
"There was an altercation in the driveway and at the doorway of the address. We just do not know if it's a random attack as such or whether someone went there for a specific reason or purpose. It's too early to say."
Mr Long says a silver Subaru station wagon was dumped at the Ohoka Road ramp on the Northern Motorway shortly after police were called but it is unclear if the two incidents are related.
However, police are appealing for sightings of the car, which was seen being driven erratically along Line Side Road.
The body was still at the scene on Saturday and Mr Long says it is unlikely a post mortem will be conducted before Monday.