The Independent Police Conduct Authority has found an officer was not justified in shooting a man dead in Auckland in February 2021.
Tangaru-Noere Turia, who was 34 and a 501-deportee from Australia, died after being shot three times.
He had been holed up in a house for a number of hours before coming out with a shotgun.
Police repeatedly asked him to drop the firearm, but he failed to do so.
The IPCA said the officer gave Turia no time to comply with the request to drop his weapon.
Chair Judge Colin Doherty said the officer had the option of waiting for a response and should have done so.
On the balance of probabilities the officer's action in shooting Turia was an excessive and unreasonable use of force, the IPCA said.
However, there was insufficient evidence for a criminal prosecution.
The IPCA said the initial response by police to the incident was appropriate and well-managed.
There was good awareness of command roles and good communication between commanders, and the cordon and contain strategy was well-executed.
However, the command team did not adequately consider the need to at least notify neighbours of the risk posed by Turia.
Police attended the scene at 5.45pm after Turia fired a shot through the living room window of the house next door. They attempted to get Turia to surrender over the next couple of hours.
At about 8.20pm, police began appealing to Turia using a loudspeaker. He immediately became more agitated, and one or two minutes after the loudspeaker appeal commenced, he walked out the front door of the house and onto the driveway holding his loaded shotgun over his shoulder.
An AOS officer was stationed at the rear of the driveway, about 25 metres away from Turia. As soon as the officer saw Turia, he challenged him to drop his weapon, and then shot him three times. About two seconds elapsed from the time Turia would have become visible to the officer to when he was shot.
"We accept that circumstances could have quickly changed and the threat posed by Mr Turia could have easily escalated and required a lethal response, but at the point when the officer fired that was not the case; Mr Turia had walked slowly out onto the driveway with his firearm over his shoulder to investigate the source of noise from the loudspeaker."
At that time the immediate risk he posed to others was low to negligible, albeit that the consequences if that risk had materialised might well have been very serious, the IPCA said.
Police to review training, policy
Police said they would review training and internal policy on the use of lethal force.
Assistant Commissioner Sam Hoyle said the report highlighted a need for greater clarity in police policy and training about thresholds for the use of such force.
"Our staff respond to a wide range of fast-changing incidents in any given day.
"Many of these involve a very real risk to the public and can require split-second decision making."
The review would be undertaken to ensure staff were adequately equipped to make such decisions, he said.
Police did not consider an employment investigation in this case would lead to a different outcome to the criminal investigation.
Police union unhappy with findings
The police officers' union rejected the IPCA's findings.
Police Association president Chris Cahill said Turia advanced on officers in an agitated and aggressive manner and the officer did not have the luxury of second-guessing what he may have intended to do.
"The association holds that any delay in acting would have placed Officer A and other police at the scene at an unacceptable risk of death or grievous bodily harm, and strongly contests the IPCA's suggestion that Officer A could not have believed that Mr Turia posed an imminent risk when he emerged onto the driveway holding a shotgun," he said in a statement.
"At best that suggestion is naïve, at worst blind to the reality of the threat an offender who had already discharged his firearm posed to the officers present.
''They had no protection, only cover of a small wooden fence that would not have stopped a blast from a shotgun. So they could have suffered death or serious injury if he had decided to fire that firearm. That's the decision the officer had to make in a very short period of time.''
Cahill said the officer involved, known in the report as Officer A, was incredibly distressed with the report's finding.
''We believe the report has not taken into account cognisance of his statement of what he said or what other officers said. It has looked at it in an unrealistic environment of the perfect scenario when you have time to look back and consider.''
He said the report was basically saying officers should wait until they were 100 percent sure that a person was going to fire a shot. "That is unrealistic. That isn't the operating environment police can live in.''
The association also rejected the IPCA finding that the officer had a pre-determined view to shoot Turia if he came out of the house armed.
Cahill was noncommittal when asked if police officers had lost confidence in the IPCA.
''It has certainly created some issues for us to work through. We are very disappointed with the findings. They have put at risk some of the officers in having to re-assess what they might do because they are concerned about negative findings from the IPCA, which is not a situation officers should be put into.''
IPCA principal operations advisor Warren Young said the IPCA simply disagreed with the Police Association view the officer was justified in shooting Turia.
Young said while the officer challenged Turia to drop his weapon, he did not give him time to do so.
''When the shots were fired Mr Turia was not presenting his firearm at anyone. He had it over his shoulder pointing backwards with the barrel in his hands.''
Young said by not giving Turia time to put down his gun, the officer clearly had a pre-determined view that Turia was going to pull the trigger.
He said there was no imminent risk at the point police shot Turia.
''We have examined where everyone was at the time and the officer who pulled the trigger knew full well where everyone was.''
On the decision not to prosecute the officer, Young said: ''In order to convict someone you need to prove beyond reasonable doubt and that means a jury would need to be satisfied as to the officer's state of mind at the time. That is quite different from finding whether or not there was any misconduct involved in his action.
''That is a civil standard and the Police Association are quite wrong about that and we think the police ought to be looking at whether it is appropriate for the officer to be undertaking this sort of role.''