Of the six people stabbed, three were in critical condition, one was serious and two were in moderate condition, according to outlet Stuff New Zealand.
"A violent extremist undertook a terrorist attack on innocent New Zealanders," Ardern said in the briefing, BBC News reported. "What happened today was despicable, it was hateful, it was wrong. It was carried out by an individual, not a faith."
"What happened today was despicable, it was hateful, it was wrong. It was carried out by an individual, not a faith."
Video taken in the store shows shoppers scattering amid the chaos.
The suspect was being watched after he was sentenced last month to one year of supervision for possession of ISIS propaganda, specifically a video of people being murdered, according to Stuff. He had been in the country since 2011, Reuters reported.
"Had he done something that would have allowed us to put him into prison, he would have been in prison," Ardern said Friday.
The government had tried to sentence him under the Terrorism Suppression Act but was denied, according to Stuff.
In his sentencing, Justice Sally Fitzgerald said the suspect had both an "operative interest" in ISIS and "the means and motivation to commit violence in the community."
The suspect, who authorities have not identified because of a court suppression order, entered a Countdown supermarket in Auckland and grabbed a large knife from a display cabinet and started to stab people, BBC reported.
Police Commissioner Andrew Coster said a police surveillance team and a special tactics group had followed the man from his home to the supermarket.
Coster said that when the commotion started, two police from the special tactics group rushed over. He said the man approached police with the knife and so they shot and killed him.
"It's obviously a very big shock, completely unexpected," the husband of a woman in her 50s who was stabbed in the hip told Stuff. He asked not to be identified. He called the attack "a bit of a nightmare" but said she is expected to be OK.
A 19-year-old witness told Stuff she saw the man's wife in the parking lot.
"She was on the phone with 111 [New Zealand’s emergency number], and then she was talking to them and then when I got to her she just dropped her phone and that's when she sat down and she was just saying ‘I'm so scared, I'm so scared,’" Monica Seve said.
She said she used the woman's sweater to apply pressure to her wound.
"I was about to wrap her wound with her sweater and then people started screaming there's a gun there's a gun and as soon as she heard that she just ran for her life."
Seve said the woman left her phone and wallet but she was eventually able to return them to her.
In March 2019, 51 worshippers at a mosque in Christchurch, New Zealand, were murdered by a White supremacist shooter.
Australian Brenton Tarrant killed 44 people at the Al Noor mosque during Friday prayers before driving to the Linwood mosque, where he killed seven more.
Imam Gamal Fouda, a Muslim leader who survived the attack on his mosque, told Stuff Friday was the country's "darkest day" since the Christchurch massacre.
"This person is brain-washed," Fouda said. "Terrorists who do such inhumane and vile acts do not belong to any religion. They act out of sheer hate, and they have no place in our country. Our first thoughts and prayers are for the victims and their families."
The Associated Press contributed to this report.