Brenton Tarrant, 28, appeared in a Christchurch District Court and was charged with murder. His hands were handcuffed and he was wearing prison clothes.
Judge Paul Kellar said although Tarrant was facing only one murder charge, it was "reasonable to assume there will be other charges".
One armed congregant pursued the gunmen who opened fire during Friday prayer at his mosque in the New Zealand city of Christchurch, firing two shots at them as they sped away, the New Zealand Herald reported.
That rampage killed at least 41 people, while an attack on a second mosque in the city not long after killed several more.
It was the deadliest terror attack in the nation's history.
Prime Minister Jacinda Ardern described the tragedy as a "terrorist attack" and noted numerous victims could be migrants or refugees.
Ardern said the victims came from across the Muslim world, with Turkey, Bangladesh, Indonesia and Malaysia among the countries rendering consular assistance.
"For these people who are victims in these mosques - they are refugees, they are people who are from our migrant communities who've chosen to live in New Zealand, thinking they would find a safe place where they could be free in their religion and their culture".
Service at a mosque in Gibsonia
"This individual has travelled around the world with sporadic periods of time spent in New Zealand", Ms Ardern said on Saturday. She asserted that New Zealand "will not and can not be shaken" by this attack. A woman who said she was a colleague of his when he worked as a personal trainer in the Australian city of Grafton said she was shocked by the allegations against him.
Players and members of the team's coaching staff were reportedly on their bus, approaching the Masjid Al Noor mosque in Hagley Park when the shooting broke out.
"We stand in solidarity with the people of New Zealand and their government against this vicious act of hate".
US President Donald Trump, who condemned the attack as a "horrible massacre", was praised by the accused gunman in a manifesto posted online as "a symbol of renewed white identity and common purpose".
He escaped out the back door and climbed over a wall when he saw people fleeing and realised what was happening.
While his manifesto and video were a clear ploy for infamy, they do contain important clues for a public trying to understand why anyone would target dozens of innocent people who were simply spending an afternoon engaged in prayer.
Children's screams can be heard in the distance as he returns to his vehicle to get another weapon.
Ardern said the shooter was "in possession of a gun licence" obtained in November 2017, and he started legally purchasing the weapons the following month.
He then walks outside to the street, where he shoots at people on the sidewalk. After walking back outside and shooting a woman there, he gets back in his auto, where the song "Fire" by English rock band "The Crazy World of Arthur Brown" can be heard blasting from the speakers. The singer bellowed "I am the god of hellfire!" and the gunman drove off before police even arrived. "I heard ... four big bangs I thought it was maybe fireworks because this [a shooting] never happens in New Zealand".
What to make of NCAA's Notice of Allegations sent to Georgia Tech
Jack, 35, played at Georgia Tech for three seasons between 2002-2005 before heading to the National Basketball Association . Georgia Tech has been hit with a notice of allegations from the NCAA regarding alleged "high-level" recruiting violations.
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