A neighbour believed those involved lived next door to each other.
"I didn't hear anything though, just when I came out about 8.30pm there was police everywhere."
Another neighbour heard an argument before the incident.
A man was standing on his balcony and yelling abuse at a man and woman in the pensioner flat next door, the neighbour said.
"She was giving back as good as she got though."
The neighbour did not know what the argument was about.
Soon after a man came to the door and asked for police to be called.
"He called through the window 'there's been an assault'."
Police officers, a police dog and an ambulance soon swarmed the pensioner flats.
A man being sought by police refused to open the door so officers smashed a window before forcing their way through the front door, the neighbour said.
"They shouted 'let us in, let us in or we'll break this door down'."
Another officer stood on a neighbouring balcony, in case the man tried to escape, the neighbour said.
Senior Sergeant Greg Sowter said the stabbing occurred after an argument escalated at the pensioner block.
Both victims, one male and one female, are over 65-years-old and have been transported to Auckland City Hospital with non-life threatening injuries.
Police said they believed the man arrested and charged was also a resident in the pensioner flats.
The charge is yet to be decided.
A St John spokeswoman said emergency services were called just before 7.30pm.
One person, an elderly woman, was transported by ambulance to Auckland City Hospital.
At the time she was in a serious condition.
Police were called to the flats just over a week ago, after a man allegedly yelled abuse at neighbours and threatened to smash one's window with a rock, the neighbour said.