New Zealand's police commissioner insists covert agents were left with no choice but to kill the Auckland supermarket terrorist.
A day on from Friday's shock attack, more detail is filtering in about the stabbing, which left seven people injured and six in hospital.
Three are still fighting for their lives in hospital in critical condition.
Two are stable and two more are recuperating at home.
The perpetrator was a 32-year-old Sri Lankan national who is likely to be named tomorrow should Jacinda Ardern's government prevail with an application to strike down a court-ordered suppression order.
The man moved to NZ to study in 2011, became known to police in 2016, and spent three years in jail prior to his release in July.
Police planned for his release, setting up round-the-clock surveillance which involved up to 30 officers at a time.
Despite the monitoring operation, he caught officers unaware by striking on Friday.
"There was nothing unusual about the subject's routine as he travelled by train to the supermarket to Lynmall," Police Commissioner Andrew Coster said.
"He was shopping normally for about 10 minutes before the attack started."
Mr Coster said police were constructing a portrait of the attack using supermarket CCTV footage.
They now know seven people were injured, not six, and the attack started earlier than first thought.
New Zealand Police Commissioner Andrew Coster says police had no choice but to fatally shoot a man who stabbed shoppers at an Auckland supermarket. Source: AAP
Mr Coster said a seventh person was injured beyond the six who were hospitalised with injuries.
"That person missed being stabbed but did suffer an injury from the knife and managed to get out the way," he said.
"He self-treated at home and we discovered him overnight."
While one eyewitness account suggested the terrorist wielded a knife as big "as a mini-sword", Mr Coster said evidence didn' support the idea he brought a weapon into the the New Lynn shopping centre.
"CCTV shows him removing a kitchen knife from the shelves in the store and a knife fitting that description was found close to him after he was shot," he said.
On Friday, Mr Coster said officers intervened within one minute of the attack.
On Saturday, he corrected himself, saying officers stationed outside the supermarket learned of the attack around 60 to 90 seconds after it began.
They intervened within one minute of hearing shouts and seeing people running - meaning the attack lasted two and a half minutes.
When officers found the terrorist, Mr Coster was adamant they needed to use lethal force.
"Absolutely. Without a doubt," he said.
"This man had attempted to kill at least six people and was advancing on them at pace with a knife. We don't execute. What we do is we remove the threat."
Mr Coster said "some of (the terrorist's) actions ... suggested that he was planning for the future".
As the terrorist was killed, there is no chance of revealing whether he planned the attack or something more horrific in future.
"There are two options here. One is that he planned it and that he was very clever in the way he planned it to make it look like normal, or that it was opportunistic and something that he did a short notice," Mr Coster said.
"We will probably never know the answer to that. We do know he was surveillance-conscious and we have been watching him carefully knowing that that he operates in that way."
Even if the attacker was alive, there would have been little likelihood of him revealing his motives or intentions.
He had refused previous psychological analysis and was highly uncooperative with authorities.
