There were no obvious warning signs when the Christchurch mosques gunman moved to New Zealand from Australia in 2017 -- he had no criminal history and was not on any security watch list.
But 29-year-old Brenton Tarrant will now go down in history as New Zealand's first convicted terrorist, and the first person in the country ever sentenced to life imprisonment without parole.
Born in the rural Australian town of Grafton, a six-hour drive north of Sydney, Tarrant worked as a gym instructor before arriving in New Zealand.
Only later did it emerge that Tarrant began amassing an arsenal of weapons soon after setting up home in Dunedin with the intention of carrying out an atrocity against New Zealand's Muslim community.
After meticulous preparation, the plan came to a ghastly conclusion on March 15 last year when Tarrant attacked two mosques in Christchurch, livestreaming the event as it happened.
"He intended to instil fear into those he described as 'invaders', including the Muslim population or more generally non-European immigrants," prosecutor Barnaby Hawes told a sentencing hearing at Christchurch High Court this week.
As the world searched for answers, former friends and colleagues were quizzed about Tarrant's background and possible motivations.
Details emerged of a socially awkward loner who became a gym junkie after being bullied as an overweight teenager.
He was also apparently hit hard when his father died of cancer in 2010 at the age of just 49 -- but there was nothing that remotely explained the searing hatred behind Tarrant's crimes.
- 'Act of revenge' -
In a rambling "manifesto" posted before the massacre, Tarrant talked of being radicalised during trips to Europe and Asia, apparently financed by an inheritance that meant he did not have to work.
An exceptional aspect of Tarrant's personality seems to be his susceptibility to online hate and, eventually, his willingness to weaponise the internet to share his killing spree on social media via a helmet-mounted GoPro camera.
Increasingly isolated in the real world, Tarrant dwelt in extremist chat rooms, sharing racist memes and in-jokes with online acquaintances who encouraged his views.
Prosecutor Mark Zarifeh quoted from an interview prison authorities conducted with Tarrant in April, when he described his state of mind at the time of the attacks.
"He said he had a poisoned emotional state and was terribly unhappy," Zarifeh said.
"He felt ostracised by society and wanted to damage society as an act of revenge."
Minutes before the massacre, Tarrant sent a message to the now-defunct extremist website 8Chan saying it was "time to make a real-life effort post".
"You are all top blokes and the best bunch of cobbers (friends) a man could ask for," he wrote.
Scrawled on his weapons were the names of numerous historical military figures -- many of them Europeans involved in the Crusades or in fighting Ottoman forces in the 15th and 16th centuries.
In court, Mirwais Waziri, who survived a bullet to the neck, punctured any self-aggrandising illusions Tarrant may have held about being some sort of racial warrior on a historical mission.
He reminded Tarrant that the youngest fatality in his attack on unarmed men, women and children was three-year-old Mucaad Ibrahim, shot twice while clinging to his father's leg for protection.
"He did not have religion, faith or colour. He didn't know anything about that," Waziri said.
"How are you going to answer that... how are you going to face God on judgement day and answer how and why you killed a three-year-old boy?"
Tarrant, despite the bluster contained in his pre-massacre manifesto, could find no words to try to justify himself, or express remorse, and he waived his right to speak at the hearing.
Noticeably thinner than the bulked-up killer who flashed a white-power hand signal at the court the day after the attacks, he remained mute and submissive as jailers led him away to serve his life sentence.