The Independent Police Conduct Authority has found the tactical decision-making by police during an armed siege near Kawerau in March 2016 was highly flawed and placed officers at risk.
The authority also found police were justified in shooting at Rhys Warren, who was found guilty for shooting at four police officers during the siege.
According to the authority, the AOS officers should never have entered the Warren family's house where Warren shot at the officers.
Authority Chair Judge Colin Doherty said the three AOS officers who fired at Warren made a lawful decision based on the circumstances that they perceived at the time.
“They fired to defend themselves and their fellow officers from an imminent threat of death and in order to manage the safe evacuation of wounded officers. However, the previous decisions which led the AOS officers to be in this position 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.”
Judge Doherty said the incident illustrates the need for police at all levels to have a thorough understanding of control and command, how command structures alter as incidents escalate in seriousness, and the responsibilities attached to key roles within those structures.
Warren since been convicted of two counts of attempted murder, three counts of using a firearm against a law enforcement officer and wounding with intent to cause grievous bodily harm.
He has also been sentenced to preventive detention.