The email is said to contain gunman Brenton Tarrant’s 87-page, 16,000-word “manifesto”, which named the mosques in the attack and said he’d selected them about three months ago.
Ms Ardern’s office said the suspect had sent the document in a mass mail-out that included a generic email address for the prime minister, the opposition leader, speaker of the parliament and around 70 media outlets.
It was sent “a matter of minutes” before the attack.
A spokesman said the email didn’t describe the specific incident and there was “nothing in the content or timing that would have been able to prevent the attack.”
The staff member monitoring the accounts sent it to parliamentary services as soon as they saw it, who sent it on to police, the spokesman said.
In the lengthy document, which Tarrant also posted online, he denounced immigrants as “invaders” and also named Donald Trump as “a symbol of renewed white identity and common purpose”.
Mr Trump immediately condemned the attack as a “horrible massacre”.
Ms Ardern said she had spoken to Mr Trump, who had asked how he could help. She said she replied to him: “My message was sympathy and love for all Muslim communities.”
She added the shooting could “only be described as a terrorist attack”, and officials are still carrying out the identification of the victims.
The majority of victims were migrants or refugees from countries such as Pakistan, India, Malaysia, Indonesia, Turkey, Somalia and Afghanistan.
Muslims account for just more than 1 per cent of New Zealand’s population.
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