Dunedin resident Jenny McDowell was doing her shopping at a Countdown supermarket in Dunedin when she heard screaming.
"I looked up and witnessed a man stabbing one of the female staff members," she said.
McDowell was one of many people inside the Cumberland St supermarket this afternoon when a man stabbed several people in what police believe was "a random attack".
Southern police district commander Paul Basham said police were satisfied they had the person responsible in their custody and he would likely be charged this evening or first thing tomorrow.
Basham praised the actions of those who intervened in the attack, calling their actions "nothing short of heroic".
McDowell has been left shaken after today's incident, where she saw a woman get stabbed in the back and helped treat a man with a stab wound on his neck.
She said at one point, people were trying to throw things at the alleged offender in a bid to distract him.
"I just saw people from the public trying to restrain the man. There would've been about three or four people, he almost got loose again.
"The man with the neck wound started bleeding quite heavily and someone yelled at me 'can you administer first aid?' I froze for a second or two. I had trained in first aid years ago. I thought I have to get something to stop the bleeding. I had a reusable bag so I emptied that out."
Before she needed to use the bag, a staff member pulled off their jersey to put pressure on the man's wound, she said.
"I was just helping to hold down the jersey to get the pressure on. The man who was injured [said] 'my wife, is my wife okay?' I just tried to reassure him help was on the way and stayed with him."
Basham addressed media following the incident at Countdown Dunedin Central which ended with five people injured, three critically.
The Southern District Health Board said five people were treated at the emergency department following the 2.35pm incident.
Four were admitted to hospital in a serious condition - three to the ICU and one to a general ward. One patient was being treated in the emergency department.
Witnesses at the scene say there was "chaos" as the attack unfolded.
A man, who had blood on him, was arrested and was walked to the Dunedin Central Police Station, next door to the supermarket.
Basham said the alleged offender was receiving medical attention in Dunedin Hospital. He was under police guard and had yet to be formally spoken to or charged.
He said it was a "fast-moving and extremely traumatic event for every person in that supermarket – the victims who were injured, those present who tried to intervene and those who had to flee to a place of safety".
"While we are satisfied we have the person responsible in our custody, we are in the very early stages of our investigation into the circumstances.
"This includes understanding the motivation for this attack which will be a key component of the investigation. However, on the face of what we currently know, we believe this was a random attack.
The actions of those who tried to detain the alleged offender while they waited for police to arrive was "nothing short of heroic", Basham said.
"The scene is currently locked down and will be the subject of an extensive scene examination."
The minimum charge was likely to be wounding with intent to cause grievous bodily harm, he said.
"I expect, depending on when he's seen at the hospital, he will come back to the police station here tonight and he will be formally charged this evening or first thing tomorrow and appear in the Dunedin court tomorrow morning, if all things go to plan."
Dunedin Mayor Aaron Hawkins said the incident was not something he would expect to unfold in his city.
"Everyone should feel safe in their place of work or going about everyday tasks like grocery shopping. These sorts of events are particularly chilling because it could have been any of us or our friends or family - it's a busy location in the centre of the city."
Prime Minister Jacinda Ardern addressed the incident at her post-Cabinet press conference today.
Police said at this stage there is nothing to suggest that this is a domestic terror event, she said.
"I have been told that there is no reason to believe that anyone else was involved.
''Needless to say such an attack is hugely concerning and I do want to acknowledge the really early reports of courageous acts by bystanders who have taken action in order to protect those around them.
''Our thoughts are with all those who have been affected by this attack."
A couple, who asked not to be named, were shopping in the aisle next to the pharmacy department, where the incident took place.
"We just heard a scream and thought someone must've fallen, but it got louder and louder and more people were screaming," the woman said.
"I saw one red hand among the people; a bloody hand, and everybody started running towards the exits."
The man said brave members of the public had pinned down the stabber but they believed he had been able to wrestle his way free before police arrived.
One woman who was shopping a couple of aisles over, said she was also alerted to the incident by the high-pitched yelling.
"I heard screaming and I thought it was just teenagers, but then I heard someone yell 'he's got a knife'."
Another woman who was entering the supermarket at the time said she was confronted by two hysterical girls.
Another bystander grabbed them, thinking they were shoplifters but they were followed by a stampede of shoppers.
"It was chaos," she said. "Unbelievable."
Staff members congregated outside the supermarket, some visibly shaking.
Police and multiple ambulances descended on the Cumberland St supermarket after the incident.
A St John spokesman earlier said four people were injured, three critically and one seriously.
An Otago Daily Times reporter at the scene said one person was put into an ambulance with an apparent neck wound.
A second person was stretchered into an ambulance. At least one of the patients is a member of staff.
A third person wearing a Countdown uniform came out with a bandaged shoulder. A fourth injured person who also appeared to be a staff member was taken out of the supermarket with what looked like head and shoulder injuries.
A person at the scene said a staff member told him two other staff members had been stabbed and that the attacker allegedly walked up to someone and stabbed them in the back.
The supermarket was evacuated and people have been told to stay away from the windows.
Police have blocked the entrances to the car park but some people were being allowed to leave the car park.
An armed police officer is standing guard outside the front entrance.
Countdown managing director Spencer Sonn said they were shocked after the attack.
"Our priority right now is our injured team members and caring for our wider team in the wake of this extremely traumatic event. We are deeply upset that customers who tried to help our team members were also injured.
"We have been concerned about the escalating violence towards our team, and this is something we have continued to talk and raise as an issue over the last year.
"Our amazing team comes to work to serve Kiwis every day, and our customers visit our stores knowing that they will be safe. We are heartbroken that this wasn't the case today.
"Our Dunedin Central store will remain closed today and tomorrow while we support our team, and we are co-operating fully with the police."
They allege the Crown ignored Treaty obligations by not engaging with them.