An Independent Police Conduct Authority investigation will likely be launched into an incident where a man was been shot dead by police after taking three children hostage in a Tauranga home.

Police said they had no option other than to shoot a man who was holding a knife to the chest of a child when they stormed his home yesterday afternoon.

The fatal shooting ended a 15-hour standoff with the man, who had earlier threatened his partner with a knife before holding three children hostage all day.

An Independent Police Conduct Authority spokesperson said the matter had been referred to the authority by police and it was likely the authority would conduct an investigation.

The spokesperson said an authority investigator was on the ground in Tauranga today and would provide a preliminary report to the authority, after which a decision on an investigation, the form of it and its scope would be made.

The spokesperson said matters to be considered and the time to complete any inquiry would depend upon the complexity, and were unknown at this stage.

New Zealand Police Association regional director Scott Thompson said different officers would process a traumatic incident differently.

"It's a tragedy that a person had to lose their lives. Cops are there to keep people and society safe."

He said support for police staff in the aftermath of incidents had improved in "leaps and bounds" in recent years, particularly with the introduction of the Critical Incident Policy.

"No one can change what happened but [action] can be made to ensure there was no more carnage."

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