"One person inside the store, a male, received stab wounds and is in a critical condition in hospital," Friend said.
"A second person received a wound to their stomach and head, and is in a less
serious condition.
Friend said it wasn't clear whether anything was stolen from the shop.The mother and her adult son received serious and critical injuries, and were in a stable condition after surgery.
Two doors down, shift manager Nancy Toora was working at Sumit Superette when customers came in and told her what had happened.
"They told me people at the dairy had been robbed and stabbed. I heard it was a mother and her son.
"I know the mother. She is really nice. They always come here to buy vegetables.
"It is really scary. It could have been me."
The father, who was normally working in the store, was away on holiday, she believed.
Police cordoned off the dairy last night. A police spokeswoman this morning said investigators worked until 4am.
Last year the former National Government announced $1.8 million worth of measures to help stricken dairies, including partial funding for sophisticated prevention methods.
The scheme was amended by the Labour-led Government, who instead announced $4000 fog cannons would be almost fully funded for about 420 businesses identified by police as high risk.
New Zealand Association of Convenience Stores executive director Dave Hooker said the level of violence in last night's attack was "disturbing".
Convenience store robberies had been increasing in recent years, which he believed was due to the rising price of tobacco.
"Over the past 24 months there has definitely been an increase. We saw about 700 in the 2016-2017 year, and this increased to about 1300 in 2017-2018.
"Dairy owners have a high level of anxiety around security."
He supported the subsidies for fog cannons, and said there had been a greater focus from police on the issue.
So far about 60-70 dairies had taken up the offer for cannons, he said.
"But I would like to see the fund used more broadly, to include things like installing bollards, CCTV, strengthening windows and improving store lighting."
Dairy owners should also have plans in place about what to do in such situations, and could take practical steps including installing LED lighting and making the shop interior more visible from the street, he said.
In March, Hamilton dairy owner Sandip Patel was left with a fractured skull and a gashed head after an attack by two masked robbers, who had an axe and a machete.
After the brutal robbery he installed a metal cage at the entrance to his shop.
Dairy strikes
• February: The owner of a dairy in northwest Auckland was hit with a wrench when three men burst into his store.
• March 14: A father-of-two needed 30 stitches for head injuries after a machete- and axe-wielding duo attacked him at his Hamilton East dairy.
• March 18: Three teenagers armed with hammers robbed a dairy in Hamilton. One of the hoodie-wearing trio held the lone shopkeeper down while the others stole cash and tobacco.
People with information regarding last night's stabbing can contact Auckland City Crime Squad on (09) 302 6557 or Crimestoppers anonymously on 0800 555 111.
