When the man got into the BMW, the officer fired three more times, hitting the back of the car. The prisoner appeared to be getting out of the car with his gun, so the officer again fired.
The prisoner then dropped the gun and drove off. He was caught hours later.
The entire shooting incident took place over 37 seconds, and no one was injured.
While there was no evidence the man fired his gun, the authority said it was reasonable for the officer to believe he was firing toward him and other officers, given an analysis of video footage of the incident and witness accounts.
Judge Colin Doherty said overall, the officer's actions were to defend people in a fast-moving situation.
But the three shots fired into the back of the car were not justified, he said.
"It is implausible to believe he perceived the man posed an immediate threat to anyone while the man was sitting inside the car, at the instant the officer pulled the trigger to fire shots six, seven and eight."
The authority also found police did not follow all procedures after the shooting incident.
Police are also changing their policy to ensure it covers officers who fire shots from slow-moving patrol cars.
In a statement, Bay of Plenty District commander superintendent Tim Anderson said this was an extremely dangerous incident and he was proud of the officers for how they acted in the fast-paced situation.
"As always, we review these incidents and take learnings from them," Anderson said.
"I am grateful that no one was injured and that our officers were able to go home at the end of their shift.
"We have ensured they have been supported following this incident."
- RNZ
