"We believe absolutely there was only one attacker responsible for this", police commissioner Mike Bush stated Monday, noting that possible support from other people is a very important part of the investigation.
The New Zealand Herald previously reported that Brenton Tarrant, a 28-year-old Australian man who killed at least 50 people in two mosques, while live-streaming the shooting, would be representing himself in court.
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Last week two mosques were rocked by shootings in the eastern New Zealand city Christchurch. The country's Prime Minister Jacinda Ardern has called the shooting a terrorist act, saying that it was the country's darkest day.
Police also detained a man and woman after finding firearms in their car. While the woman has been released, the man has been charged with illegal actions associated with firearms.
A third detainee has been charged with incitement to racial discrimination and will face trial on Monday.