Two other people were being held in custody and police said they were trying to determine how they might be involved.
Three of the arrests are believed to be directly related to the attacks, with the fourth's involvement still being determined.
Bush said he would not at this time "be discussing the offenders' possible motivations or the causes of this incident".
"Forty-eight patients, ranging from young children to adults with gunshot wounds are being treated at Christchurch Hospital". The attacks seem to be a carefully planned and the authorities detained four people and defused explosive devices that are said to have belonged to the attackers.
Congress president Rahul Gandhi on Friday condemned the mass shootings in New Zealand that killed 49 people and termed it "a despicable act of terrorism". Police have urged users not to share the distressing footage and they are working to have any videos removed. And those values will not and cannot be shaken by this attack.
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After many had spoken, Trump dramatically signed his veto message and then held the document up for the cameras to capture. He described the Congressional attempt to stop him as a "dangerous" and "reckless" resolution that was "against reality".
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Jahan had taken to social media to post screenshots of Shami's alleged affairs with other women. The BCCI not only gave him a clean chit but also reinstated his central contract.
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As the Saudi delegation left the conference, many members felt that Saudi Arabia had managed to avoid scrutiny for too long. Saudi Arabia has accepted as many as 453 human rights recommendations, either full or in part, during the past 10 years.
Bush confirmed the shootings had resulted in "multiple fatalities".
The commissioner said police had been dealing with two shootings at two mosques in Christchurch, one at Deans Avenue and one at Linwood Avenue.
Compounding the horror of Friday's massacre in New Zealand: Video emerged online that appeared to be bodycam footage of the suspect firing his weapon.
"I particularly want to express my honest prayers and thoughts to those New Zealanders and Australians of Islamic faith today who have been the victims of this callous right-wing extremist attack", Morrison said at a press conference on Friday afternoon local time.
The attacks in Christchurch, in which 40 people were killed, were reportedly live streamed on several social media sites by the shooter and have since been used in broadcasts and shared on social media. "We're also removing any praise or support for the crime and the shooter or shooters as soon as we're aware", she said.
Stay tuned for more updates on this developing story.