As New Zealanders struggled to cope with the deadly terror attacks in Christchurch, stories of heroism have emerged from the tragedy, including a worshipper who chased away the gunman armed only with a credit card machine.

Fifty people were killed on Friday and dozens more injured. But the police and eyewitnesses say a second attack by 28-year-old Brenton Tarrant was partly thwarted by Abdul Aziz, 48, who was born in Afghanistan.

Aziz said he charged at Tarrant outside the Linwood mosque when someone shouted that a gunman had opened fire.

Tarrant had already killed dozens at the Al Noor mosque nearby, and on the streets.

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"He had on army clothes. I wasn't sure if he was the good guy or the bad guy. When he swore at me, I knew that he's not the good guy," Aziz told Reuters.

When he realised the mosque was being attacked, he ran towards Tarrant, picking up a credit card machine as a makeshift weapon.

Tarrant ran back to his car and got another gun. Aziz said he threw the credit card machine, ducking between the cars as Tarrant opened fire.

"When I was ducking between the cars I could hear my two boys were saying, 'Daddy please come back inside, please come back inside', I told them 'you guys hold out, I'll be alright'."

He then picked up a gun dropped by Tarrant and pulled the trigger, but it was empty. Aziz told the shouted at the attacker, hoping to draw his attention to himself and away from the mosque.

Aziz said Tarrant went inside the mosque, and he followed, eventually confronting the gunman again.

"When he saw me with the shotgun in my hands, he dropped the gun and ran away toward his car. I chased him," he said.

Aziz threw the gun he was carrying at Tarrant’s car, smashing the window.

Aziz said four of his children were with him at the mosque when the attack occurred.

Nearly 100 Muslim worshippers who had taken cover in the mosque as the rampage unfolded were left unharmed.

Aziz said when he came back to the mosque, everyone was frightened.

"Brothers get up, he is gone he is no more here. He is gone," he told them.

The attack is the worst ever peacetime mass killing in New Zealand. Tarrant was arrested within 36 minutes after the attack started. He was charged with murder on Saturday.

Aziz said police who arrived after the shooting blocked him from re-entering the mosque, thinking he might have been the gunman as he was seen earlier with the weapon.

"For a long time, I didn't know if my kids were alive or dead or injured because I couldn't go inside the mosque," Aziz said. He later found out all his sons had survived.

Aziz arrived in Australia as a child refugee. He lived in Sydney for almost three decades before moving to Christchurch two-and-a-half years ago.

He says he has nothing but contempt for the attacker.

"A lot of people tell him he is a gunman. But... a man never hurts anybody. He is not a man -- he is a coward," Aziz said.

He said he was overwhelmed by the outpouring of support from his neighbours after the attacks.

"There's very nice people around here. When I went home last night, my wife told me all the neighbours, they sent flowers... cards, foods, cakes. They showed all their love.

"That's why I love New Zealand -- you won't get that sort of love and that sort of respect anywhere."