The spokesperson said an authority investigator was on the ground in Tauranga todayand 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."