One has been identified as a male in his late 20s has been charged with murder and is expected to appear in court tomorrow.
One witness, who did not want to be named, said he was driving by the scene and saw a man with a "with his 3 or 4-year-old daughter" who had been shot in the back.
Police called for people not to share the video, which showed the gunman shooting repeatedly at worshippers from close range.
Bush said police had found two improvised explosive devices in one auto, a clarification from an earlier statement that there were devices in multiple vehicles.
National carrier Air New Zealand canceled at least 17 flights in and out of Christchurch, saying it couldn't properly screen customers and their baggage following the shootings.
Muslims account for just over 1 percent of New Zealand's population, a 2013 census showed. "There were three in the hallway, at the door leading into the mosque, and people inside the mosque", he said.
"It's a big mosque and there were more than 200 people inside". He said one was slightly injured.
"I saw dead people everywhere". Hospitals said children were among the victims.
Source Astro Awani
Australian Prime Minister Scott Morrison on Friday confirmed the attacker at the Masjid al Noor mosque was an Australian.
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.
None of the four people arrested were on New Zealand's security and terrorism watchlist.
One man, with blood still on his shirt, said in a television interview that he hid from the gunman under a bench and prayed that he would run out of bullets.
The YouTuber is now the most subscribed to person on the platform and since another channel has been very close to taking that number one spot from him for a while, the words used by Tarrant had become pretty much a meme, as well as a way for people to support the Swedish entertainer.
Christchurch city council offered a helpline for parents looking for kids attending a mass climate change rally nearby. The white supremacist revealed he was inspired by Norwegian mass murderer Anders Breivik, who killed 77 people in 2011.
When asked why they weren't on any lists, Ardern said: "It's an indication they had not acted in a way that warranted it".
He described Christchurch as a "very peaceful city" that is still getting over the devastating 6.3 magnitude quake that hit in 2011.
"That (earthquake) brought all the skyscraper buildings down and this is one of the reasons why people are fearful, I feel", he told CNN.