On January 30, 2019, the terrorist-to-be emailed himself a to-do list. Over the next six weeks he intended to clean out his rented house in Dunedin, decorate his many guns, and scrub evidence from his computers.
"15th march is go," the last line of his note began, "do rain or shine".
The night before this date, Brenton Harrison Tarrant called his mother and sister in Australia and talked for nearly two hours. He told them both he loved them.
This was unusual, notes the Royal Commission of Inquiry report into the terrorist attack of March 15.
"His sister told the Australian police than the individual said that he loved her - in fact said this twice - which was unusual. Although the individual did sometimes tell her that he loved her, he usually only said this when about to leave on a long trip."
As it turns out it was raining in Christchurch on the morning of March 15. The showers cleared by noon, only resuming at night in a mirror of the torrent of grief that flowed from the events that afternoon at the city's Al Noor and Linwood mosques.
Events of that day have now been well-canvassed in court, following proceedings that saw Justice Cameron Mander hand down New Zealand's first-ever life-without-parole sentence for committing 51 murders.
This Royal Commission report into the lead-up to those events - both the actions of Tarrant and those of public agencies which might have noticed red flags - is both deep and broad. It spans nearly 800 pages and draws on sources ranging from an interview with Tarrant in prison to reports from intelligence agencies in countries like Austria and Poland.
The report plots Tarrant's radicalisation pathway - germinated in a broken childhood in Australia, and fermenting in dark corners online - and painstakingly lays out what is assessed as years of planning.
Biographical details - of a bullied childhood, exposure to domestic family violence and an inability to form domestic or sexual relationships - mark Tarrant as a typical lone-wolf terrorist who mistakes being an outcast with martyrdom.
Family members flagged him as racist from his early teens, and he appears to have only grown more virulent as he found those of a like mind on the Internet. And it wasn't the notorious sites he used most often - the report concludes he spent most of his time on YouTube.
He also started frequenting notorious internet site 4chan from the age of 14. Until early 2017 he was active, under a pseudonym, on the far-right Australian United Patriots Facebook page.
He donated A$139 to Freedomain Radio, the YouTube channel and podcast of right-wing provocateur Stefan Molyneux. Later that year he donated thousands to European political parties operating under the extremist Generation Identity banner. He gave bitcoin, multiple times, to US-based neo-Nazi publisher the Daily Stormer. He set up a Trade Me account with the handle Kiwi14Words - a fairly blunt neo-nazi reference.
The royal commission report rubbishes Tarrant's manifesto as propaganda, noting the specific terrorist attacks by Islamists in Europe he claimed to be taking revenge for actually post-dated the start of his own terrorist planning.
In the immediate aftermath of the arrest he is said to have told police he was a member of Anders Breivik's order of the "reborn Knights Templar" there were "nine more shooters".
But his explanation of the day's events only ever mentioned himself, and European intelligence agencies concluded his - and Breivik's - reference to the Templars was fantastical.
Copies of the manifesto of Breivik - another far-right terrorists who killed 77 people in Norway in 2011 - were found on Tarrant's digital devices and the document was referenced in his own manifesto. The report says Tarrant took inspiration from Breivik - down to following advice about how to avoid drawing the attention of authorities and enhancing his size and stamina by repeatedly injecting himself with steroids and testosterone.
All this detail in the report will be invaluable for researchers and policy-makers around the world grappling with a surge in right-wing extremist violence, of which Tarrant is both a symptom and a cause.
But the report has a seeming aversion to assigning specific blame for any public failings, instead pointing to broader problems at intelligence agencies which had de-prioritised the growing threat of right-wing extremism, and blandly noting police did "not meet required standards" when issuing Tarrant a firearms licence.
This issuing of a licence is probably the clearest point where Tarrant could have been stopped early, with police required to interview both the applicant and two nominated referees to ensure they are a fit and proper person.
The report says he was close to his sister, and had told her he thought he might be "autistic and possibly sociopathic," and in mid-2016, following travels abroad, his sister said he was a "changed person" and was now regularly talking about the Crusades.
In October 2017 she was listed as a referee by Tarrant as part of the firearms licensing process - but was not accepted by police as her residence in Australia meant she could not be interviewed in person.
Tarrant instead substituted her with someone he'd met through online gaming, and the licence was granted and allowed him to legally assemble an arsenal.
March 15 was chosen, it seems, largely because Tarrant's financial reserves - generated from his dead father's asbestos-death payout - were dwindling.
By the start of 2019 Tarrant's final plans were firming.
His mother came to visit him in Dunedin in early January. He refused to eat at what he called a "migrant cafe" after seeing it was staffed by people of colour. He talked of moving to the Ukraine and only wanting his money to go to "white New Zealanders". He tried taking his mother to the firing range, but was unable to unlock the gate.
On her return to Australia, Sharon Tate said she was "petrified" about her son's mental health and increasingly racist views". Authorities only became aware of these concerns when the Australian Federal Police came knocking in late March - too late.