>> READ ALSO. Attacks in two mosques in New Zealand: what we know and what we don't know yet
The alleged attacker, a 25-year-old Australian, was arrested and charged with murder.
Australian Prime Minister Scott Morrison described the shooter as a "extremist, right-wing and violent terrorist".
Attacks live broadcasts on social networks
The attacker broadcasts the images of his attacks live on social networks, where he is seen passing from victim to victim, shooting the wounded at close range while trying to escape. The images are "extremely painful"New Zealand police warned.
The authorities have warned Internet users that they could incur up to 10 years in prison in case of sharing.
This video posted on Facebook Live, made with a camera apparently attached to the shooter's body, shows a short-haired white man with short hair driving his car to the Masjid al-Nour mosque.
We then see him enter the building and shoot the faithful passing from room to room.
In addition to the video, which the AFP has verified authenticity but will not publish, the shooter-related photos have been published on social networks showing semi-automatic weapons covered with the names of the characters in military history, including the Europeans who fought the Ottoman forces in the 15th and 16th centuries.
Racist "Manifesto" published on Twitter
Before acting, the man, who looks like a white man from the low-income working class, posted on Twitter at "Manifest" racist 74 pages from the title "The great substitute", referring to a theory born in France and popular in far-right circles, according to which "European peoples"would be "Substituted" from non-European immigrant populations.
The document describes two years of radicalization and preparations. He claims that the decisive factors in his radicalization were the defeat in the 2017 French presidential election of right-wing leader Marine Le Pen and the death of little Ebba Åkerlund at the age of 11 in the 2017 ram-ram attack in Stockholm.
The Twitter, Instagram and Facebook accounts where the videos, photos and manifest were published have been suspended.
Appearance in court this Saturday
He is scheduled to appear Saturday in the district court of Christchurch.
Two other men are in custody, without anyone knowing what is blamed for them.
Mass killings are rare in New Zealand, which strengthened its arms transport laws in 1992, two years after a man with psychiatric problems killed 13 people in the South Island.