UPDATE 3:15PM: THE bus driver killed in this morning's attack at Moorooka has been identified as 29-year-old Manmeet Alisher.
The Brisbane Times identified Mr Alisher as a prominent member of Brisbane's Indian community.
He only began working as a casual bus driver a few months ago.
Detectives have launched a homicide investigation into his death and a 48-year-old man believed to have attacked Mr Alisher is in custody.
Queensland Police Commissioner Ian Stewart addressed media this afternoon and said there was no evidence the attack was linked to terrorist activity.
He said police also did not believe the attack was racially motivated.
"Over the course of this afternoon and the next few days, police will be talking to witnesses," he said.
Commissioner Stewart urged any witnesses to the incident to come forward.
He also spoke on two other tragic incidents, including a murder investigation in The Gap after a woman's body was discovered and the deaths of four people at Dreamworld earlier this week.
"We've rarely had a week where so much tragedy has occurred," he said.
"We will do our absolute best to ensure that the investigations are completed as early as possible.
Moorooka investigation is still live. Person assisting did throw something at bus driver. Driver now deceased. @CoPStewart— QPS Media Unit (@QPSmedia) October 28, 2016
UPDATE 2.09PM: THE death of a bus driver in Moorooka this morning has now become a homicide investigation.
Queensland Police announced this afternoon that detectives had started a homicide investigation into the man's death.
"Preliminary inquiries indicate just after 9am passengers were boarding a bus on Beaudesert Road when a man has thrown an item at the driver causing a small fire," QPS said.
"A 48-year-old man was arrested at the scene and is currently assisting police with their enquiries."
Brisbane City Council told media earlier today it would offer counselling to the city's bus drivers.
Queensland Premier Annastacia Palaszczuk told Brisbane Times the week had been one of tragedy for the state.
Authorities are praising the actions of a taxi driver who was parked near the bus at the time of the fire.
Aquek Nyok kicked in the rear door of the burning bus to allow passengers trapped inside to escape.
Six people were taken to hospital and treated with smoke inhalation.
This taxi driver, Aquek Nyok, kicked in the door & saved passengers from the Moorooka bus fire. Deserves credit. pic.twitter.com/DNOwIe9u1N— Emily (@Emilitaa23) October 28, 2016
EARLIER: A 29-year-old bus driver is dead after a passenger doused him in flammable liquid and set him alight.
Another 11 passengers on the Brisbane bus who witnessed the incident had to be treated by paramedics for smoke inhalation and minor injuries.
Earlier reports of the incident suggested there had been a crash which resulted in the bus catching fire.
But shortly after 11.14am, Queensland Police Superintendent Jim Keogh said the bus stopped into the Moorvale Shopping Centre to pick up three passengers when the person struck.
"At that time that one of the passengers entered onto the bus and poured a flammable liquid onto the driver," Supt Keogh said.
"Subsequently the driver was set alight and is now deceased.
"The fire was substantial, he would have stood little chance.
"Our inquiries indicate it was rather rapid, a lot of finer details won't be known for some time."
The superintendent described it as a "horrific incident", adding that a 48-year-old man is in custody.
Those on board were "visibly shaken".
"Police are speaking to passengers, as you can imagine they are traumatised," he said.
"We are providing assistance in that regard.
"A bus driver going about his business, supporting the community and has his life taken from him in a senseless and needless act."
Supt Keogh added that terrorism did not appear to be a motive.
"I have been confronted with many situations but this is a rare one, with no apparent motive," he said.
"We are not alleging a robbery."