"I have asked our agencies this morning to work swiftly on assessing whether there was any activity on social media or otherwise, that should have triggered a response".
Tarrant also appears to have posted a link to a manifesto on a now-deleted Twitter account and the online forum 8chan where he spoke of his hatred for Muslim immigrants in Europe.
A video of one of the shootings was live streamed on Facebook by a man identifying himself as Brenton Tarrant.
Worshippers, possibly dead or wounded, lay huddled on the floor of the mosque, the video showed. Reuters was unable to confirm the footage's authenticity and police urged people not to view or share it.
Friday's mass shooting has renewed calls for a tough crackdown on New Zealand's gun laws in a country where there is one firearm to every four people.
A police spokesperson in the Australian state of New South Wales said Tarrant's family have been "assisting and cooperating" with authorities.
Wahb noted that the attacker had written the name of the Quebec City mosque shooter on his weapon, "so that actually triggers the sad feeling and the sorrow of this tragedy that happened here because we actually experienced it with a city that is close by here".
Ardern said that investigators are working to determine whether two others who were taken into custody in relation to the massacre were directly involved.
Commissioner Mike Bush hailed the "absolute bravery" of both police and members of the public "who put themselves in harm's way" to apprehend the suspect. Tarrant was also a legal gun owner and used legal means to acquire the five guns used in Friday's attacks, according to Ardern.
Still, Muslims were advised to stay away from mosques while the nation's security alert remained at the second-highest level a day after the deadliest shooting in modern New Zealand history. This, according to her, allowed the Australian terrorist to legally obtain the weapons in December 2017, and that he was not on any watch-lists prior to the attacks.
"This is not the New Zealand they know", she said.
AOS push back members of the public following a shooting at a mosque in Christchurch New Zealand Friday
The hospital also confirmed 39 people are still receiving treatment, with 11 of them in intensive care.
Funerals were planned on Saturday for some of the victims, several who were born overseas.
Yousef Wahb, Imam of youth, education and outreach, speaks on Friday about the 49 people killed at two mosques in Christchurch, New Zealand, while the president of the Windsor Islamic Assocation, Mirza Baig, left, looks on.
Mourners write condolence messages in chalk along the footpaths in Christchurch.
"I was running and there was a guy [who] said there was a shooting in the mosque so I was running, while I was running there was a lady being shot", he said. "It's very grave, it's very serious", he told reporters. In New Zealand, commentators also anxious that the horror would sow deep divisions in a society that has largely avoided the polarizations that have spread elsewhere. One man, 18-year-old Daniel Burrough, has been charged with incitement.
Christchurch Mayor Lianne Dalziel said graves were being dug as city officials worked closely with the community on the specific requirements of a large number of Muslim funerals.
Political across Asia and the Middle East voiced concern over the targeting of Muslims.
Western leaders from Donald Trump to Theresa May expressed solidarity with New Zealanders, deploring what the White House called a "vicious act of hate".
Prime Minister Jacinda Ardern described the tragedy as a "terrorist attack" and noted numerous victims could be migrants or refugees.
One man who said he was at the Al Noor mosque told media the gunman was white, blond and wearing a helmet and a bulletproof vest.
"He had a big gun.He came and started shooting everyone in the mosque, everywhere", said the man, Ahmad Al-Mahmoud.