The 32 yo man who stabbed six people in Countdown LynnMall on Friday arrived in New Zealand from Sri Lanka in October 2011.
The "ISIS-inspired" extremist, who currently has name suppression, came to the interest of New Zealand police in 2016, after he posted "staunchly anti-Western and violent" material on the internet, according to the New Zealand Herald.
After this incident in 2016, the man, who lived in the west Auckland suburb of Glen Eden, was given a formal warning by police, but continued to post violent material.
Prime Minister Jacinda Ardern says the reason he continued to be surveilled by national security agencies is suppressed, but is working to share that information with the public.
"We have used every surveillance agency we could to keep Kiwis safe," she said during a press conference following the incident on Friday.
The man reportedly told a worshipper at his mosque he planned to join Isis in Syria, then was caught at Auckland International Airport after booking a one-way ticket to Syria in May 2017.
Police reportedly searched the man's home, and found material that glorified violence, including images of him posing with an air rifle, and a hunting knife hidden under his mattress.
He was detained in custody without bail for more than a year and eventually pleaded guilty to charges of distributing restricted material. Because of the length of time S had already spent in custody, he was sentenced by a High Court judge to supervision, the New Zealand Herald reports.
Both Ardern and Police Commissioner Andrew Coster insisted during the press conference that officials did everything they could to keep the terrorist in prison.
"We have utilised every legal and surveillance power available to us to try and keep people safe from this individual," Ardern said.
"The fact that he was in the community will be an illustration of the fact that we haven't succeeded in using the law to the extent we would've liked. That is why he was being closely monitored at all times.
"By law we could not keep him in prison. If he'd committed a criminal act that would've allowed him to be in prison, that's where he would have been. Unfortunately, he didn't."
Ardern revealed she had personally known about the extremist for "some time".
The Prime Minister also maintained that although the man followed IS ideology, he was a "lone wolf" terrorist.
"It was carried out by an individual not a faith - not a culture, not an ethnicity - but an individual ideology that is not supported here.
"He alone carries the responsibility for these attacks. Let that be where the judgement falls."