A police response to a man firing shots at officers in Kawerau in 2016 was "highly flawed", the Independent Police Conduct Authority (IPCA) has found.
Rhys Warren fired shots at a police officer and a marked police aircraft involved in a cannabis removal operation on March 6, 2016, and the Armed Offenders Squad (AOS) was called out.
By 1pm the AOS was in position around two rural properties on Onepu Spring Road, calling for the occupants to come out. After receiving no response, six officers and a police dog entered Warren's family home to arrest any occupants.
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Warren was in a bedroom and fired three shots at the officers, seriously injuring three of them. The officers fired 46 shots back and evacuated the house. Later that afternoon Warren shot another officer who was positioned on a cordon near the house.
The IPCA found that while police were justified in shooting at Warren in the circumstances, police should never have entered the house and there was "poor general understanding" among officers about how control and command should have operated.
"The lack of proper oversight was a strong contributing factor to the flawed tactical decisions," the IPCA said in its report.
Warren surrendered to police the following morning, and has since been convicted on two counts of attempted murder, three counts of using a firearm against an officer, and wounding with intent to cause grievous bodily harm.
IPCA chair Judge Colin Doherty said the officers fired at Warren "to defend themselves and their fellow officers from an imminent threat of death and in order to manage the safe evacuation of wounded officers".
But he said the decisions that led to this unfolding were "highly flawed".
"Better decision making is likely to have prevented these officers from having to make the decision to use their firearms in the first place. Just as importantly, it would have prevented the officers from being in a position of considerable risk."
Police have accepted the IPCA findings and said its own internal reviews are consistent with the report.
Police assistant commissioner for districts Bill Searle said incidents such as what happened at Kawearu are "complex and dynamic".
"Circumstances can and do change very quickly and decisions have to be made based on the information available to officers at the time. The safety of our staff and members of the public is a strategic and operational priority for Police. The fact four officers were injured in this incident is of great concern to us."
He said despite the problems identified by the IPCA, "the person responsible for shooting our staff was Rhys Warren who has been sentenced in court to preventive detention".