The man allegedly behind a horrific stabbing rampage at central Dunedin supermarket was a frequent customer who had caused problems by "flipping out" before.

Police this morning said they had charged a 42-year-old man with four counts of attempted murder following yesterday's events at Countdown.

The man was released from hospital last night and moved to Dunedin Central Police Station.

He is scheduled to appear in the Dunedin District Court this afternoon.

Several people told the Otago Daily Times the man was a known troublemaker who was regularly in and around Countdown.

A staff member said he was a regular visitor to the supermarket who previously caused trouble there.

Another person said he had seen the alleged attacker around town, saying he was a troublemaker.

He recalled him losing his temper and "charging" at someone in a previous incident.

A frequent Countdown customer said he was down at the supermarket "every day flipping out" and was always "screaming at people".

"Glad he's off the streets," the person said.

"I see him around a lot, off his face ,he shouldn't [have] been in the public to start with."

He said he was such a frequent visitor that Countdown knew him by a nickname.

He believed he had seen him hanging around Countdown for the last six months.

Corrections officer amongst victims

A corrections officer is one of four injured in yesterday's violent knife attack in a Dunedin Countdown supermarket.

The man and his wife were inside the Cumberland St store in central Dunedin when a man with a knife allegedly attacked four people, including two supermarket workers.

Corrections southern regional commissioner Ben Clark this morning confirmed one of those injured was an employee.

Clark said the service was focused on ensuring the staff member, their family and colleagues had all the support they required during a stressful and difficult time.

"We would like to thank the emergency services, police and supermarket staff for the help they provided following the incident.

"To respect the privacy of our staff member and their family, we will not be providing any further comment."

It is believed the Corrections officer worked at the Otago Corrections Facility and his wife, who was alongside him in the store, was a nurse.

One of the employees injured in the attack was believed to be the store's manager.

Anne Coulthard told the Herald he was a long-time friend and worked alongside him at the beginning of his career in the late 1990s.

"I have seen and watched him grow from a young teenager to a wonderful store manager. And always looked forward to seeing him when I shopped there, we often laughed about days past when he was so much younger."

Coulthard, a former supermarket worker herself, said it was a sad day when such a tragic event happened in Dunedin.

The injured manager had previously worked at Countdown Andersons Bay in South Dunedin.

This morning police said four people remained in hospital. Three of the injured were in a serious but stable condition. A fourth person was in a moderate condition.

with text by NZ Herald