A coroner has criticised the actions of police officers who confronted an armed man, saying their mistakes had a snow-balling effect that ended in him being shot dead.
Police chased Lachan Kelly-Tumarae's car for 18km before he stopped next to an urupa and pointed his gun at them in Omahu, near Hastings, in 2011.
An officer then fired 14 shots at the 19-year-old, hitting him four times and fatally wounding him.
The Independent Police Conduct Authority found last year that police were justified in shooting Mr Kelly-Tumarae, but criticised the officers for not complying with some policies.
That included the actions of the second police car to arrive at the cemetery, which breached protocol by pulling up right next to Mr Kelly-Tumarae's car instead of stopping at a safe distance.
In findings released on Friday, coroner Peter Ryan said he agrees with the IPCA criticisms.
Mr Ryan said by pulling up next to Mr Kelly-Tumarae, the officers limited their tactical options to a single possibility - confronting him.
"Those officers' actions initiated a chain of events that had a 'snowballing' effect - [the two officers] placed themselves in danger of being shot; this caused [another officer] to step out from the cover of his police vehicle and advance upon and challenge Lachan."
He said that then prompted Mr Kelly-Tumarae, still holding the shotgun, to stop and turn towards the third officer.
"This caused [the officer] to believe he had no other option but to shoot Lachan."
However, Mr Ryan found that despite those mistakes, it was in response to Mr Kelly-Tumarae's actions in aiming the shotgun at the police several times.
He said it would remain a mystery as to why Mr Kelly-Tumarae had taken the shotgun and what he was planning to do with it.
Mr Kelly-Tumarae's grandmother, Narina Tumarae, told the inquest that her grand-son had been upset by a conversation with a relative earlier in the day but he was happy when she saw him later that evening.
In her evidence, Mrs Tumarae also said that she believed he hadn't intended to hurt anyone with the gun, and had stopped at the urupa because it was where seven generations of their whanau were buried.
Police said they've improved the tactical training programme for nearly 6,000 front-line staff, in response to the coroner's recommendation.