Two Children Died at a School Mass. The Gunman Idolized Mass Killers Online.

A gunman killed two children, ages 8 and 10, and wounded 17 others at a Catholic school Mass in Minneapolis on Aug. 27. Videos he uploaded to YouTube that morning, and that were later removed, displayed a handwritten manifesto and firearms inscribed with the names of past mass shooters — the latest attacker steeped in an online world that venerates them.

On the morning of Aug. 27, a gunman opened fire during a school-wide Mass at the Church of the Annunciation in Minneapolis, killing two children and wounding 17 other people before dying of a self-inflicted gunshot wound, authorities said, according to CNN. Police identified the shooter as Robin Westman, 23, a former student at the parish school.

The children killed were Fletcher Merkel, 8, and Harper Moyski, 10. Fletcher was remembered by his family as a boy who loved to fish and cook; Harper was known for her laughter and kindness, NBC News reported. Fourteen children and three adults were injured, the F.B.I. said.

Videos posted, then pulled down

Shortly before the attack, an account attributed to Westman uploaded videos to YouTube that displayed a handwritten journal, or manifesto, and an arsenal of guns and ammunition, CNN reported. The account was taken down, but not before the footage began to circulate.

The videos appeared to have been posted the morning of the shooting and were timed to publish around the time of the attack, police said. Extremism researchers who examined the material said its purpose was less a coherent political message than a bid for infamy — a performance built for an online audience, NPR reported.

A catalog of past killers

The firearms and magazines shown in the videos were covered in writing, including the names of previous mass shooters. Analysts who reviewed the footage told NPR that the shooter had studied earlier attackers in detail and emulated their online personas, part of a well-documented pattern in which perpetrators cast themselves as the next entry in a lineage of killers.

Among the attackers referenced in the writings and inscriptions were the gunman who killed 51 worshippers at two mosques in Christchurch, New Zealand, and the man who murdered 11 people at the Tree of Life synagogue in Pittsburgh, according to CNN. The material fixated repeatedly on school shootings and on the perpetrators of earlier massacres.

‘A hate-filled ideology’

The F.B.I. said it was investigating the shooting as an act of domestic terrorism and a hate crime targeting Catholics. The bureau's director, Kash Patel, said evidence indicated the attack was “an act of domestic terrorism motivated by a hate-filled ideology,” and that the shooter had left anti-Catholic references in the manifesto and on the firearms, expressed hatred toward Jewish people, and written a call for violence against President Trump on a magazine, as reported by NPR. Investigators said the shooter appeared to have acted alone.

An online pipeline for the next attacker

Researchers who track violent extremism said the case fit a fast-emerging pattern in which young people are drawn into diffuse online networks that trade in mass-shooter footage, images and lore, glorifying past killers and, in the process, priming the next one, NPR reported. The videos in this case were removed, but only after an attack they were built to accompany.

It is a sequence platforms have confronted before. Content that celebrates atrocity spreads fastest in the minutes after it is posted, and moderation, however swift, tends to arrive after copies have been made. Each attacker who leaves behind a curated online record becomes source material for the communities that venerate them — a loop that researchers and law-enforcement officials say has become one of the defining features of contemporary mass violence, according to CNN.