Within hours of the massacre that killed 50 people, New Zealand Prime Minister, Jacinda Ardern, promised to change the country's gun laws, though she didn't immediately specify how.
"This is not New Zealand", she told a group at the city's refugee centre.
Two other people were in custody and police said they were seeking to understand whether they were involved in any way.
New Zealand Police Commissioner Mike Bush said more charges would be laid.
One of the images most widely shared on social media in solidarity with New Zealand is a cartoon of a kiwi, the country's national bird, crying.
The court was closed to the public over safety concerns, however a number of people gathered outside ahead of his appearance, including a man who told reporters his father was one of the victims.
New Zealand law enforcement is working with Australian intelligence and police in the "wide-reaching" investigation, the commissioner said. She also says New Zealand will make "weekly compensation" available to victims' dependents on an ongoing basis.
A Candelit Prayer is held outside the State Library of Victoria on March 16, 2019 in Melbourne, Australia; 49 people are confirmed dead, with with 36 injured still in hospital following shooting attacks on two mosques in Christchurch, New Zealand on Friday, 15 March at the hands of suspected shooter Brenton Tarrant.
The youngest person missing and feared dead is three years old, Greenhill tells NPR's Weekend Edition.
During a Saturday press conference, Ardern said the gunman had two semi-automatic weapons, two shotguns, and a lever-action firearm (five firearms in total).
Ms Arden stated the deadly attacks was one of New Zealand's "darkest days" and vowed to change the country's current gun laws. Story continues after video. Tarrant did not apply for bail, and per ABC News reports, did not apply to have his name suppressed.
'But the Prime Minister has signaled that we are going to look at that issue [banning semi-automatic weapons]'. Residents were mandated to turn in their semi-automatic rifles and other now-outlawed weapons.
Police Association President Chris Cahill backed tighter gun laws, saying the weapons used in the mosque shootings were banned in Australia after the Port Arthur massacre in 1996 in which 35 people were gunned down.
It was just over a year ago that Kim Kardashian called for safer gun laws in the U.S. following the mass shooting at Marjory Stoneman Douglas High School in Florida.
Ardern said she had spoken with Trump, who asked how he could help.
The message, received less than 10 minutes before the attack on Friday, did not set out what was about to happen, he said. "These acts of hate have no place in the diverse and tolerant society for which New Zealand is justly known", the White House statement said.