Australia's Prime Minister Scott Morrison confirmed one of the suspects is an Australian-born citizen.
Gray also said she recalled that Tarrant's father Rodney died from some kind of asbestos-related illness when Tarrant was finishing high school. "At this point in time we should never make assumptions", he said.
"These are people who I would describe as having extremist views, that have absolutely no place in New Zealand, and in fact have no place in the world", the prime minister said.
Here is what we know about the attack. Some 200 people were estimated to be in the building at the time of the incident, resulting in the deaths of some 41 people.
Survivor Syed Mazharuddin told the New Zealand Herald that he was praying with about 60 to 70 people at the Linwood mosque when he heard gunshots. "Four are in custody, three of them are men and one is a woman", commissioner Mike Bush said, saying there were "significant" and "multiple" fatalities. Police had one person in custody but they were not sure if others were involved, and people should stay away from mosques.
They also report that at the second mosque, a prayer goer returned fire with a rifle or shotgun.
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New Zealanders are trying to come to grips with the worst massacre in their nation outside of wartime in more than 200 years.
She said there police have got no reason to suspect there might be others out there, but they have not ruled it out.
The Linwood Avenue mosque is one of two which have subject to a shooting, with another taking place at a mosque on Deans Avenue. "What happened in New Zealand is a crime against humanity".
"It is clear that this is one of New Zealand's darkest days", Ardern said during a press conference on Friday afternoon. "We stand in solidarity with the people of New Zealand and their government against this vicious act of hate".
"Many of those who would have been directly affected by the shooting may be migrants to New Zealand, they may even be refugees here", Arden told reporters.
"A man who lives near the Masjid Al Noor mosque in central Christchurch said many people were dead there".
The Prime Minister also offered strong words in defence of a now hurting New Zealand: "This act is not a reflection of who we are as a nation. this isn't who we are".