A man at the centre of a major police incident pulled a woman from her car at gunpoint and led police on a dramatic chase through inner Auckland, witnesses said.

Police called a 2.30pm press conference to give updates about the "critical incident".

Assistant Commissioner Richard Chambers said when the Auckland event unfolded, the Eagle helicopter was in the area and spotted a car being driven erratically.

The car crashed and police fired a shot.

Chambers said a member of the public was rescued by a person caught up in the drama.

A police chase started, with police and the Eagle chopper following the driver.

The driver put everyone at risk, with the car crashing with a second car, taken from a member of the public, Chambers said.

The driver was seen pointing a gun at a person.

Chambers said the vehicle had crashed into another car at an intersection and the man held a gun at the other driver's head.

"The offender got out and approached the driver waiting patiently at the lights and held the firearm at that person's head."

• Firearm pointed at police: Gunshots reported at major incident in Auckland
• Deadly overnight stand-off: One killed after Hamilton police shooting

He was shot by police.

Chambers said the man at the centre of today's shooting had been a "person of interest" to police. He had been wanted by police "for some time".

Chambers described the actions of police as courageous.

"My staff have done a remarkable job today."

Chambers said those who were involved in the shooting were not from the specialist armed offenders' squad.

"They've done a remarkable job today to take [on] someone presenting a real risk to members of the community."

He described the events as "volatile, high risk and dangerous" situations.

He appealed for footage from bystanders to help with the investigations.

Chambers said the first car was stolen from a Church St car yard. His staff were looking for another person who may have been involved in stealing the car from the yard.

As the person stole the vehicle, it rolled over the foot of a member of the public, said Chambers.

He said it had been a volatile and fast-moving situation. Police had tried to make sure the public and themselves were safe. It was a challenging situation at a busy location where the events unfolded.

He said support was being offered to those who had a firearm held to their head while someone was trying to steal their car. Chambers described the ordeal as one of the worst days of their lives.

The Hamilton incident

Earlier in the press conference, Chambers updated details about the shooting that happened in Hamilton last night.

At 7.50pm police went to an address in Hillcrest, concerned for the safety of a person in possession of a high-powered weapon, he said.

The person wasn't at the initial address, but when they returned they opened fire on police, he said.

Police returned gunfire and the man was fatally injured.

He died a short time later.

Chambers revealed a police officer was injured, after falling over and striking his head.

He was undergoing surgery today.

Chambers said the man who died last night was from Hamilton.

Police had concerned he was going to use the high-powered weapon against people.

Sadly as a result of what occurred last night he lost his life," said Chambers, adding his staff did their best to save him.

Chambers said the dead man fired on police at least five times.

IPCA investigations are underway into both incidents, he said.

Chambers said the situation in both Auckland and Hamilton had been traumatic for police.

Earlier report: Auckland shooting

One person was seriously hurt and another has moderate injuries after witnesses on Church St East in Penrose reported hearing gunshots before 11am today.

Witnesses have described seeing a "largely built man" speed through Ellerslie in a white BMW X5 with no plates, before crashing into a kerb on Great South Rd in Penrose.

The man leapt from the BMW and ran straight towards a motorist waiting at the nearby traffic lights, a witness called Steve said.

Pointing his pistol at the female driver, he then pulled her out of the car, said Steve, who didn't wish to give his last name.

The woman appeared to kneel on the ground with her hands on her head as the man carjacked her Suzuki and threw a "wild" U-turn before speeding in the direction of State Highway 1 on-ramp.

Police had their weapons trained on the man but appeared unwilling to fire with innocent bystanders nearby, Steve said.

"You have to admire their bravery," he said.

"They didn't shoot, which is a good thing given how tightly packed cars are at that intersection."

A worker at Youth Garage said two people were involved in the theft of the BMW, later involved in a police incident on Great South Rd.

"A lady came in first, tried to be like a customer, checking around," Dali Hou said.

"Then she came back again, checking cars again. I think about that time she stole our key and then she went out again and a guy came over and just drove it out … yeah, teamwork."

Hou wasn't at the car yard when the incident happened but had spoken to the yard's director who had tried to stop the man leaving in the BMW, and had to move to avoid being struck.

No weapons were shown by either the man or woman, Hou said. He had been told they were aged in their 30s or 40s.

The car was taken when the director went to get some information from inside.

"When he came out, they were going."

The car, a 2013 or 2014 BMW S5 was "nothing special", Hou said.

"It's just kind of cheap … we have for $14,800".

The director of the yard, who was nearly run over as the couple - the man driving - was okay.

"He never saw a weapon."

Two intersections on Great South Rd in Penrose remain closed.

One at Great South Rd and Church St/South Eastern Highway and another at Great South Rd and Campbell Rd, Auckland Transport said.

Another witness called Sonia also reported seeing a man brandishing a firearm running down Great South Road, weaving in between cars.

The man pointed his weapon back at three chasing officers, who were shouting at him to stop, said Sonia, who didn't wish to give her last name.

"He was pointing a firearm at the cops and trying to run. I could hear them shouting but my window was up and I needed to get out of there."

Another witness said he saw a white BMW X5 with no plates speed through Ellerslie, "travelling 100km/h in a 50km zone."

The BMW then hit a kerb at speed, at which point it "caught air", the witness said.

The car's airbags deployed and police were able to capture a "large-build man", who had been driving, the witness said.

Unconfirmed reports allege the BMW may have been stolen from a dealership.

St John said they were alerted to the incident at 10.59am.

One person was seriously hurt and taken to Auckland Hospital, while a second patient was taken to Middlemore with moderate injuries, a spokesman said.

Sonia saw the police chase unfold while pulling up to the lights at the Z petrol station on Great South Road.

The man appeared to be holding a pistol, she said.

She was worried the man with a firearm might run through the petrol station.

Her first thought had been to "get out of there" and get home to her children, she said.

She also saw a number of cars U-turn from the area to try and get away. She also reversed away from the area and travelled home on an alternative route.

A cafe manager on Church St East said his customers were sitting outside when they heard gunshots.

They didn't see the incident, the cafe manager said.

But after hearing the shots they went out onto the road to see what had happened and saw a swarm of police cars at what they thought was the site about 150m further down on Great South Rd.

A worker near the Church St intersection told the Herald she heard sirens and a number of police cars "swoop in".

She also saw an ambulance and a helicopter, which has since left the area.

Drivers are being urged to delay their journey or use an alternative route.

Assistant Commissioner Richard Chambers will provide the latest detail on the incident, as well as more information about the fatal police shooting in Hamilton last night, at 2.15pm.