A bus driver has been killed in Brisbane after a passenger boarded the vehicle and "set him on fire", police allege.
The passenger allegedly doused him in a flammable liquid then set him alight. It did not appear to be terrorism-related.
Queensland Superintendent Jim Keogh told reporters: "There is no apparent motive. We're not alleging robbery - this is the senseless, needless taking of a life going about supporting the community by providing transport."
A 48-year-old man was taken into custody. Keogh said he was "compliant" with officers who aided the arrest.
A homicide inquiry was underway, he said.
"The bus pulled in for the purpose of picking up passengers at the stop, there were six people on board at the time," he said.
"It was at that time that one of the passengers boarding the bus entered the bus, poured a flammable liquid on the driver and was set alight."
Asked if there was any suggestion the two men knew each other, Keogh said there was nothing to suggest a connection.
"It would appear random."
Six "deeply traumatised" passengers have been taken to hospital to be assessed, mainly for minor injuries like smoke inhalation.
They were lucky to escape with their lives from the "substantial" fire. Some were already on the bus and others were at the bus stop where the arrested man had been waiting.
A taxi driver told the Courier Mail he busted down the back door of a bus to allow passengers to escape the inferno.
Aguek Nyok, a local cab driver that had stopped to get a haircut, said he saw the bus erupt into flames.
"Literally as I pulled up I saw and heard the front of the bus explode and a guy ran out and he was covered in flames, head to toe," he said.
"All the people were at the back trying to get out of the bus but they couldn't get out the front because of the flames."
Keogh said the driver's actions were "heroic at the very least" and he praised the response by others who tried desperately to help.
Other onlookers said they could hear terrified screams coming from the bus.
A shop owner tried to put the blaze out with a fire extinguisher but the fire kept starting again - and the driver was still trapped inside.
Clair Savage, who was in a shop nearby when the scene unfolded, saw Mr Nyok bash down the door.
Ms Savage told the Courier Mail she saw the bus pull up and saw people screaming for help inside.
She ran out and saw Nyok repeatedly bashing the door to give way to panicked passengers.
The shop owner ran outside with a fire extinguisher but the flames "kept reigniting, with the driver trapped inside."
Police investigations are continuing at the scene.
Cab company speaks
Brisbane's Yellow Cab company have confirmed the cab driver, Nyok, is a part of their fleet, and "are not surprised" by his heroic actions.
"I agree with the police that he's a hero," said Yellow Cab general manager Bill Parker.
"I'm not surprised because this is not unusual for drivers of our fleet to be out there in the community.
"Unfortunately someone has passed away and that's very sad."
It is understood the company was yet to speak to Nyok as he is still talking to police.
"We like to believe we're part of the social structure of our community," Mr Parker told news.com.au.
He said he was "not surprised" by Nyok's quick thinking and said the company's specific cab driver first aid training was crucial to drivers' development.
"They're not trained to fix a broken leg but they're trained how to recognise if someone is having medical trauma," Parker said.
"They have saved peoples' lives in the past but nothing as horrific as this."