Suspected Christchurch terrorist Bernton Tarrant apparently vowed to kill Muslims a day before the attack - and was praised after the heinous act by his followers on social media.
An anonymous user thought to be Tarrant wrote on notorious right-wing blogging website 8Chan on Thursday: 'I will carry out an attack against the invaders, and will even live stream the attack via Facebook.'
He shared a link to a video so his supporters in other timezones could watch the massacre and said: 'By the time you read this I should be going live.'
In a reference to the Viking version of heaven, Tarrant added: 'If I don't survive the attack, goodbye, godbless and I will see you in Valhalla'.
Tarrant also posted images of his ammunition and weapons on social media before his attack.
But he was not picked up by police because he was not on the terror watchlist.
Prime Minister Jacind Ardern confirmed in a press conference: 'Those, as far as I am advised, currently in custody were not on security watchlist.
'It is a question if they were known from a security perspective. They were not on any active watchlist.'
Tarrant also told his followers to read his 73-page manifesto that he posted online so that he could be remembered.
The post was written under an anonymous name but was widely circulated on social media by Tarrant's fans.
Once the attack began, fans cheered him with statements such as 'HEIL BRENTON TARRANT.'
After the news broke on social media and television, his followers began making threads about the attack and praising him for his role in the massacre.
One user said 'Haha m*****s got f*****g rekt lol.'
Another said 'Holy f***, this is amazing.'
Other users went into far more detail with their support for the Christchurch shooter.
One praised him as a hero and went so far as to elude that they wish to commit a similar atrocity to that of Brenton.
'This man had a great body, good life, ability to settle down and live calm life, but he chose to be a f*****g hero,' a user said.
'God bless you Brenton, you were one of us and we shall drink one together if I die death of an hero.'
Another user said they were 'sad' that only up to 40 Muslims had been killed by Tarrant.
'Sadly he didn't get nearly enough of them,' the user said.
Another user thought that every man should go into a mosque and mercilessly kill innocent people.
'If every man had his dedication and determination, we'd be living in a much better place,' the user said.
'And for that alone, I salute him.'
Four people have been arrested over dual mosque attacks which left 49 dead and 48 injured on New Zealand’s 'darkest day'.
A gunman, who identified himself as Brenton Tarrant from Grafton in New South Wales, stormed the Al Noor Mosque in Christchurch on the country's South Island about 1.30pm, opening fire with a semi-automatic shotgun and a rifle on hundreds of defenceless worshippers attending Friday prayers.
A sickening 17-minute video of the unfolding horror shows the self-confessed white supremacist dressed in army fatigues firing mercilessly at people scrambling to flee, and calmly re-loading when he runs out of bullets.
At about the same time, there was a second shooting at Masjid mosque in Linwood, where seven more were killed.
In the aftermath of the bloody attacks, three men and one woman were arrested, with police charging 'one man in his late 20s' with murder.
One of them was arrested while wearing a suicide vest, while a man wearing military fatigues was arrested outside Papanui High School.
Of the 49 fatalities, 41 were killed at the Al Noor Mosque and seven at the Linwood Avenue mosque. Three were outside the mosque itself. A 49th died in hospital.
A further 48 people were rushed to Christchurch Hospital with gunshot wounds, 20 in a critical condition.
New Zealand was placed on 'high alert' following the attacks.