Key Points:

The man who allegedly sparked a pursuit in Auckland on Friday which resulted in an innocent courier driver dying from a police gunshot will appear in court tomorrow.

The 50-year-old man was taken into custody on Friday evening, shortly after Halatau Naitoko was shot after being caught in the crossfire as police tried to stop the gunman who allegedly tried to hijack a vehicle on the northwestern motorway.

A man injured during the shootout says he would be dead if it wasn't for the police action.

Richard Neville, a 40-year-old blacksmith, was hit in the arm with shrapnel during the incident on the North-Western motorway. Courier driver Halatau Naitoko, 17, was killed when hit by a bullet from a police-issue rifle.

"He was a very angry man, very desperate and very very firm about what he wanted to do," Mr Neville told TV3.

"So he raised a sawn-off rifle and from what I could see was pretty much directed at me - he'd taken aim at me."

Mr Neville had been driving along the motorway when the gunman allegedly jumped the median barrier and stood in front of his truck.

"He was trying to get into my truck. He was trying the handle and bashing on the window with the rifle and was very desperate."

Mr Neville attempted to run the man over.

He earlier told the Herald on Sunday he saw the man's expression quickly change.

"I saw his mood change from being intentful and purposeful to wanting out, looking for a way out."

The man then allegedly jumped on the back of the truck and again pointed his gun at Mr Neville.

He slammed his foot on the brakes while armed offenders squad members moved in.

"They were issuing commands and a split second after that there was just gunfire."

Mr Neville said he was hit in his arm with shrapnel, which felt like "hot bee-stings".

He stood by the actions of the AOS officers.

"They did their job. If they hadn't done their job, I wouldn't be here.

"So I thank the New Zealand police."

Police spokeswoman Noreen Hegarty said the gunman was discharged late this morning from Auckland Hospital, where he had been under police guard since Friday evening.

"He is being held in custody at the Henderson Police Station today where he will be formally interviewed about the events leading up to his arrest on Friday afternoon," she said.

Ms Hegarty said the man would appear in Auckland District Court tomorrow, on Auckland Anniversary day.

She said he would face charges relating to several alleged offences in numerous Auckland and west Auckland suburbs before the fatal shooting of Mr Naitoko.

The 50-year-old's release from hospital comes as family members of Mr Naitoko expressed dismay at the fact his death came from a police bullet.

His fiancee, Stephanie Cook, the mother of Mr Naitoko's young child, told the Herald on Sunday she was furious at police for what had happened.

"They should have been more careful. It is going to take more than apology. They have taken away my daughter's father - she is never going to know him. She will never know what a wonderful person he was."

Ms Cook said she would like the officer who fired the fatal shot to tell her how they would feel "if their partner or their father was taken away by mistake".

"I am so angry I hope they get what's coming to them."

Mr Naitoko's mother was more forgiving about the incident, saying she would try to forgive the officer involved, while his father was also angry.

"It is just unprofessional. It was a shootout on a busy motorway - they got the wrong guy and they didn't protect the public," Kepu Tepu Tepu said.

Auckland Assistant Commissioner Steve Shortland confirmed yesterday that the bullet which hit Mr Naitoko had come from one of two guns which had been fired during the incident.

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

It was not yet clear whether the bullet was a ricochet or hit Mr Naitoko directly.

The Police Association said while it was a tragic outcome, the officers involved also needed support.

"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," president Greg O'Connor said.

"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.

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

Mr Naitoko's body is due to be released to his family tomorrow.

Police historian Susan Butterworth told the Herald on Sunday that Mr Naitoko was the first innocent bystander killed by police in New Zealand.