A tradesman who witnessed people 'running for their lives' outside Masjid Al Noor Mosque has told how he rushed to nurse a wounded young girl on a footpath after she was shot alongside her dying father.
The man, who was not identified, was driving past the mosque with his colleagues when he heard 'rapid fire' and saw people taking cover.
'We saw these people hit the ground, they were being shot in front of us,' he told Radio New Zealand.
He then drove up to the scene using his vehicle to block off the street before rushing to help.
The tradesman nursed a young girl, who he assumed was just five years old, who had been shot alongside her father as it took 10 to 15 minutes for emergency services to arrive.
'We managed to get the five-year-old on the back of one of the vehicles before the ambulance came, she was critical,' he said.
The man and his fellow contractors remained at the scene for more than an hour, even while the shooter remained at large.
The tradesman witnessed the shooter leaving the mosque, chasing people who attempted to run away.
'While my worker was nursing one of the victims there was more shots inside the mosque. We were very vulnerable but in a situation like that you don't think about yourself.'
The shooter, who identified himself on Twitter as 'Brenton Tarrant' from Grafton, New South Wales, stormed into Masjid Noor Mosque in Christchurch around 1.40pm local time, gunning down dozens while hundreds of worshipers took part in Friday prayer.
'The guy was wearing like an army [suit]. He had a big gun and lots of bullets. He came through and started shooting everyone in the mosque, everywhere,' Ahmad Al-Mahmoud told Stuff.
'They had to smash the door - the glass from the window and the door - to get everyone out.
'We were trying to get everyone to run away from this area. I ran away from the car park, jumping through the back [yard] of houses.'
Al-Mahmoud said the man was 'wearing a helmet' and must have fired 'hundreds' of gunshots.
Another survivor, identified only as Nour, told the New Zealand Herald the gunman shot multiple worshipers outside before carrying out his rampage inside the mosque where he shot people indiscriminately.
'I saw people drop dead in front of me. I was crawling to get away,' he said. 'It was hitting the walls.'
Nour said he was able to flee the carnage by jumping through a broken window.
Four people are now in custody, including three men and one woman. One of them was arrested while wearing a suicide vest.
A bomb was also found in a grey Subaru Legacy three kilometres from the scene of the shooting on Strickland Street.
In a livestream video, shot by the gunman himself, he is seen in his car wearing military-style body armour and a helmet saying 'let's get this party started'.
In a 73-page manifesto he posted Twitter before the killings, he described himself as a 'regular white man' and referred to the shooting as a 'terrorist attack'.
He then drove to the mosque listening to folk music and military tunes before parking in an alley around the corner.
After retrieving one of at least six guns stored in his car, he walked up to the front door and began firing.
Mohan Ibrahim was inside the mosque and said he thought the sound of the shots was 'an electric shock' until he saw everyone running.
He is 'scared' for his friends, many of which were still inside.
'I still have friends inside. I have been calling my friends but there are many I haven't heard from,' he said.
There have also been reports of another shooting nearby at Linwood Masjid mosque.
The gunman was said to have had 'a lot magazines' strapped to his legs.
A Christchurch man told the news outlet he was awoken by the sound of '20-40' gunshots followed by a man with a bullet wound who had ran into his home to take shelter.
'I had to deal with that really quickly considering I just woke up,' Zinzan Hawke told the Herald. He said he was able to hear the shots from 5km away.
Hawke said he and his three roommates called the ambulance while they tried to treat the seven-centimeter wound on the Muslim man's leg by applying pressure.
'He didn't see the armed gunman but he heard bullets ringing around, one had just missed his stomach area. He would have had a far more serious injury in that case,' Hawke said the man told him.
Another witness said he ran behind the mosque to call the police after hearing the gun go off.
'I heard the sound of the gun. And the second one I heard, I ran. Lots of people were sitting on the floor. I ran behind the mosque, rang the police,' the man told Stuff.
'I saw one gun on the floor. Lots of people died and injured.'
Police have urged people near the area to stay indoors and report suspicious behaviour, describing the incident as 'critical'.
One man inside the mosque at the time of the shooting said there were 'bodies all over me.'
A man who escaped the mosque during the shooting said he saw his wife lying dead on the footpath.
'My wife is dead,' he said while wailing.
The shooter said he was inspired by other shooters including Anders Breivik who killed 77 people in Oslo, Norway in 2011.
He said he 'disliked' Muslims and hated those who had converted to the religion, calling them 'blood traitors'.
The shooter said he originally wanted to target a mosque in Dunedin, south of Christchurch, after watching a video on Facebook.
'But after visiting the mosques in Christchurch and Linwood and seeing the desecration of the church that had been converted to a mosque in Ashburton, my plans changed,' he wrote.
'The Christchurch and Linwood mosques had far more invaders.'
The mosque has capacity to hold more than 300 people. The total number of deaths has not been confirmed.
The Bangladesh cricket team - who are currently on tour in New Zealand - were inside the mosque praying at the time of the shooting and were forced to flee for their lives, ESPN reported.