Key Points:

The killing of an innocent man by armed police during a confrontation with an armed man in Auckland yesterday was a tragedy, but police were given very little choice about their actions, the Police Association says.

Association president Greg O'Connor said the thoughts of all police officers were with the family of 17-year-old courier driver Halatau Naitoko, who was killed in crossfire on the Auckland motorway.

"That Mr Naitoko was hit by a police bullet is a doubly cruel blow not only for his family, but also for police.

"The Police Association is unequivocally supporting the police officers involved, who were forced to act and do the best job they could when faced with a very difficult situation."

Mr O'Connor called on the public to support not only the Naitoko family, but also the police officers involved.

"It is important that we understand the situation the police found themselves in.

"They had no choice but to respond to the very serious threat posed by the rampaging armed offender. The outcome is tragic for all concerned but these are sometimes the harsh realities of policing, he said.

"It is (a) sad reality that dangerous and violent criminals put the lives of others at risk every day."

Mr O'Connor said very occasionally, in the heat of dangerous and volatile situations police are called to deal with, bystanders were accidentally dragged into the action with tragic results.

"We offer our deepest condolences to Mr Naitoko's family," he said.

Mr Naitoko, a courier driver whose partner is pregnant with twins, died in a flurry of shots, some fired by two police officers and some fired by the armed man. Post-mortem results released earlier today indicated that the fatal shot was fired by police.

The victim was working instead of his mother, who is due to give birth to her tenth child on Monday.

His mother told TV3 she was supposed to be driving the courier van yesterday but her son had told her to put her feet up "because I'm due to have a baby on Monday".

"I was supposed to go with him but then he said stay home, he can do it by himself."

She said her son was always cheerful and willing to help.

"I think that's what we are going to miss the most here, is his smiling face.

"No matter how hard the job is ... he's still going to do it with a smiling face."

She was not angry about what had happened, saying only God knew what had happened.

It was not yet known if it was a clean shot or if the bullet ricocheted off something before killing Mr Naitoko, Auckland Assistant Commissioner Steve Shortland said at a press conference today.

Mr Shortland said the homicide investigation into Mr Naitoko's death established that five shots were fired by police.

"The firearms used by police at the motorway scene were seized yesterday and all spent rounds have been accounted for," Mr Shortland said.

"Right now, Superintendent George Fraser is visiting Halatau's family to inform them of the investigation findings so far.

"There's no easy way to say what we must say to the Naitoko family, who are suffering greatly today."

Police Minister Judith Collins also expressed her sympathies to Mr Naitoko's family.

"I am deeply saddened, and today offered my sincerest condolences to Halatau's family," Ms Collins said.

"As a parent, I can't begin to imagine the pain and sadness they must feel at the loss of their beloved son, brother and father.

"I have been assured by the Prime Minister (John Key) that the Government and its agencies will provide whatever assistance and support they can to help the family through the days and months ahead."

Ms Collins said she had confidence investigations would establish how the incident unfolded and prevent a similar tragedy from occurring in the future.

Mr Shortland said the officers who fired rounds at the fatal motorway scene had identified themselves to the homicide investigation team and had given accounts of their actions.

"They are yet to be formally interviewed and those interviews will be carried out by staff who are coming to Auckland from out-of-district, specifically to carry out those important tasks."

Regardless of who fired the fatal shot, yesterday's events were "tragic for all concerned", Mr Shortland said.

"They are no less tragic today for the Naitoko family and are more tragic for the officers involved who, it must be remembered, were where they were doing their duties because a man with a loaded gun chose to rampage throughout the region without regard to anyone's safety."

The alleged offender, a 50 year-old man , was wounded by police and underwent surgery this morning to have shrapnel removed from his chest and back. He remains under guard in Auckland Hospital.

He has been charged with a firearms offence.

Another man injured during the shooting, Richard Neville, was treated at Auckland Hospital yesterday and discharged.

Mr Shortland said many people had witnessed some of the events of yesterday's hour-long pursuit and had given accounts to investigators.

However, he asked for all witnesses who had not already contacted police to do so.

Police Association head Greg O'Connor said the officers had been put in a difficult position by the alleged offender.

The Independent Police Conduct Authority was investigating the incident and an officer from outside Auckland, Detective Inspector Peter Devoy, will head the police investigation.