Police were called to the Coast Rd property at 3.20pm, Detective Inspector Stu Harvey said.
The injured man was rushed to Christchurch Hospital by helicopter.
Later that afternoon, at least half a dozen police officers, including a member of the armed offenders squad, were involved in the arrest of a man about 20km south of where the incident took place.
The victim was in a "stable" condition last week, according to family members.
