Police said the offender was known to the victim and left the scene in a dark coloured vehicle.
Detective Sergeant Shelley Ross said a forensic scene examination and a search warrant at a nearby property had been conducted but police were still looking for a weapon.
The victim had originally been transported by ambulance to Palmerston North hospital before being transferred to Wellington in a critical condition.
"A family member called the ambulance," said Detective Sergeant Ross. "There was no delay in getting him medical attention."
Anyone with information relevant to this investigation is asked to Detective Sergeant Vine on (06) 210 2233.
Alternatively information can be provided anonymously via Crimestoppers on 0800 555 111.