There were signs the 16-year-old, armed with a kitchen knife, had been radicalised online, state authorities said, adding they received calls from concerned members of the local Muslim community before the attack, which occurred late on Saturday night.
The attack, in the suburb of Willetton, had “hallmarks” of terrorism but was yet to be declared a terrorist act, police said.
“At this stage it appears that he acted solely and alone,” Western Australia Premier Roger Cook told a televised press conference in the state capital Perth, regarding the attacker.
The victim, stabbed in the back, was stable in hospital, authorities said.
Prime Minister Anthony Albanese said he had been briefed on the incident by police and intelligence agencies, which advised there was no ongoing threat.
“We are a peace-loving nation and there is no place for violent extremism in Australia,” Albanese said on social media platform X.
The attack on the bishop came only days after a stabbing spree killed six in the Sydney beachside suburb of Bondi.
Gun and knife crime is rare in Australia, which consistently ranks among the safest countries in the world, according to the federal government.
