ABC News in Australia has identified the gunman as Brenton Tarrant.
Bush told a news conference that a man has been charged with murder and will appear in court tomorrow. He said he was not a member of any organisation, but had donated to and interacted with many nationalist groups, though he acted alone and no group ordered the attack.
Earlier police said they were responding to an incident involving an "active shooter". However, Bush didn't mention the other people. Nearby place of worship, Linwood Masjid, was attacked soon after. As of 5:47 p.m. local time (12:47 a.m. ET), authorities said that a lock down of local schools had been lifted.
The security threat level is now at the second-highest level.
"We also cooperate with law enforcement to facilitate their investigations as required", it said. "I feel absolutely sickened having my name uttered by this person".
Multiple people have been killed and numerous injured.
The twisted shooter claimed to be "just a ordinary White man, 28 years old".
It appears these platforms can not keep up, as people re-upload and repost the footage, allowing it to quickly spread around the internet, effectively amplifying the shooter's hate.
Where did the shootings take place?
Bush urged anyone who had meant to visit a mosque in New Zealand not to go, to "close your doors until you hear from us again".
PewDiePie reacts to one of the New Zealand shooter calling him out on Facebook.
He tweeted: "Our hearts go out to the people of New Zealand following the news of this bad act in Christchurch".
There are also reports of shots fired at other locations in the city.
The Indonesian Embassy in Wellington sent a team to Christchurch that is coordinating with New Zealand officials.
"It is clear that this can only be described as a terrorist attack. My honest condolences to the families of victims and all of #NewZealand".
At the time of writing, the official death toll stands at 49.
Seven people died at the Linwood mosque and one died later on of their injuries at a nearby hospital.
Police Commissioner Mike Bush has urged people not to travel to mosques "anywhere in New Zealand" tonight.
A social media account had also posted a number of pictures of a semi-automatic weapon covered in the names of historical figures, many of whom were involved in the killing of Muslims. He said he considered it a terrorist attack. So far, four suspects are in custody in connection with the attack.
"What has happened in Christchurch is an extraordinary act of unprecedented violence", Ms Ardern wrote on social media.
"They may even be refugees here".
Police keep watch at a park across the road from a a mosque in central Christchurch, New Zealand, Friday, March 15, 2019.
No details were immediately available.
Residents were advised to stay indoors and notify authorities if they see anything suspicious. "I heard what I thought was fireworks and I saw a bunch of fellas running down the street. But as I say, please remain in lockdown".