A 13-year-old boy, the front passenger of the vehicle, got out and ran away, before a police officer chased after him and shouted at him to stop.
The boy, who eventually turned around and faced the officer, had a hammer in his hand and the officer tasered him.
"The authority is satisfied this was a reasonable and proportionate response to the threat the boy posed, but the boy was subsequently restrained by three officers, during which he felt kicks to the head," its report said.
A witness also saw the teenager being kicked in the head by one of the officers.
Authority chairman, Judge Colin Doherty, said: "The boy initially presented a threat to police when he confronted one of the officers with the hammer. However, once he was restrained on the ground by three officers, that threat diminished.
"There was no reason to kick the boy in the head area and this was an excessive use of force.
"However, the authority is unable to determine which of the two arresting officers administered the kicks."
The authority also found that the boy's parents were not informed of his arrest sooner due to a misunderstanding between Napier police and Hastings custody staff.
While in police custody he received appropriate medical care.
Police acknowledged the IPCA's findings into officers' actions during the arrest.
Hawke's Bay Area Commander Inspector Jeanette Park said police come to work every day to keep the community safe, and are often required to make decisions to ensure that safety for the public and for our people.
"Police take any complaint regarding staff conduct seriously, and any information is investigated thoroughly."
Through a police investigation based on evidence available, police were not able to establish whether the boy's injuries were as a result of any use of force other than the force the officers stated they used to restrain the boy during his arrest.
After the incident, police staff were debriefed, and lessons learned had been implemented, Park said.
