A man with critical abdominal injuries, believed to be a gunshot wound, walked about 1km from his home to another house in the middle of the night to get help.
The 37-year-old man knocked on a door in Manurewa at 3.40am today, Inspector Willie Taylor said.
Detective Sergeant Eddie Sutherland said it was believed the man, who has gang connections, walked from his house, where he lived in a sleep out, to the 41-year-old woman's house.
"It is thought that an altercation has taken place, leaving the victim with critical abdominal injuries.''
A Middlemore Hospital spokeswoman said this afternoon the man was in a critical but stable condition following the surgery.
"At this stage it is unclear what has occurred. We have been unable to speak to the victim prior to him going into surgery. We would like anyone with information regarding this incident to contact police immediately,'' Mr Sutherland said.
Mr Taylor said the man was unknown to the people at the house he turned up at.
There had been no reports of gun shots heard in the area overnight, Mr Taylor said.
Police were investigating the scene and talking to neighbours.