The Prime Minister is considering legal options to deport Brenton Tarrant, but says the alleged gunman will face justice in New Zealand.

Jacinda Ardern has confirmed her office received his manifesto minutes before the attack on Friday.

On Sunday she comforted a community in mourning, adding flowers to the mounting tribute outside Wellington's Kilbirnie Mosque.

She visited the mosque after receiving a briefing from her top officials, and is considering options to kick Tarrant out of the country.

"In cases where you have seen deportation, it's generally at the conclusion of a sentence being served," she told media.

He's not going anywhere until he's faced justice here.

"Absolutely charges and the trial itself will happen in New Zealand. As for the remainder, I'm seeking advice," she says. "He will certainly face the justice system of New Zealand."

The Prime Minister confirmed hers was one of 70 email addresses sent a manifesto from the alleged gunman nine minutes before the attack took place.

"Had it provided details that could have been acted on immediately, it would have been, but there unfortunately were no such details in the email."

There are reports of some details about the locations of the attacks in the manifesto itself.

"By the time any of those emails or details were passed on, [police] were already receiving those 111 calls and responding, and someone was then taken into custody within 36 minutes," Ardern says.

On Sunday afternoon, Police Commissioner Mike Bush doubled down and defended the police response time.

"Within six minutes, armed police staff were on the scene," he says.

Alongside the act of terror, the gunman committed a further sick act by sending a manifesto with information hidden in deranged ideology that arrived too late.

Newshub.