The 19-year-old California man detained by police after a hate-motivated shooting at a synagogue near San Diego claimed to have been motivated by the deadly attack on two mosques in New Zealand last month.
Police in the US said the gunman, named as John T Earnest, opened fire inside the synagogue in Poway, about 30 kilometres north of San Diego, killing one person and injuring three others including a rabbi.
While no motive for the attack on Saturday has been confirmed, the San Diego county sheriff, William Gore, said investigators were reviewing social media posts and an “open letter” published before the attack.
Posted to online forum 8chan and littered with antisemitic and racist language, the document was similar to one published on the same website by the suspect arrested after the mass shooting inside two mosques in Christchurch, New Zealand last month.
The document’s author, who identified himself as John Earnest, claimed to have been motivated by the Christchurch massacre and another shooting at Pittsburgh’s Tree of Life synagogue in which a white supremacist killed 11 people.
The latter was the deadliest attack on the Jewish community in the history of the United States. The Poway shooting came exactly six months after the Pittsburgh shooting.
Mirroring the New Zealand shooter in format and tone, the document cited biblical verses and white nationalist conspiracy theories while also claiming responsibility for a fire at a mosque in the nearby city of Escondido last month.
Graffiti discovered on the driveway of the mosque following the fire had mentioned the Christchurch attack, and police said on Sunday that Earnest was being investigated in relation to the incident.
The document also referred to a live video stream and linked to a Facebook page, an indication that the author may have tried to broadcast the shooting in the same way as the Christchurch terror suspect.
Gore said the gunman burst into the Chabad of Poway synagogue shortly after 11.20am local time and opened fire with an “AR-style” semi-automatic rifle before fleeing.
There were indications that the gun might have malfunctioned after firing numerous rounds inside the synagogue, the sheriff said.
The San Diego police chief, David Nisleit, said Earnest called 911 shortly after the shooting and surrendered to police. When an officer reached the man on a roadway, “the suspect pulled over, jumped out of his car with his hands up and was immediately taken into custody”, Nisleit said.
The attack comes six weeks after a lone gunman shot 50 people dead at two Christchurch mosques. The shooter, who faces 50 charges of murder in New Zealand, was later discovered to have links to the far-right Identitarian movement in Europe.
Following the shooting the New Zealand prime minister, Jacinda Ardern, moved to ban semi-automatic weapons from the country.