A detective has dramatically described aiming his gun at the head of Bourke Street killer James Gargasoulas from two metres away after he drove onto Melbourne CBD footpaths, hitting pedestrians.
Detective Senior Constable Aaron Diwell told an inquest into the deadly 2017 tragedy police followed Gargasoulas as he made a wild turn into Bourke Street, avoiding stop sticks deployed about 30 metres ahead of his car.
The detective pursued the offender as an air wing officer told police radio: "He is going to kill someone. Someone needs to take him out."
More than 100 people crowded in Bourke Street mall dived for cover as the car crossed an intersection and continued onto the footpath, mowing down pedestrians.
A police van then approached, causing Gargasoulas to stop as critical incident response team members piled out.
Sen Const Diwell said he ran from his car and heard loud bangs.
He saw the suspect in the driver's seat leaning across the passenger side and identified him as Gargasoulas.
"I drew my firearm and pointed it at his head through the front passenger window. I yelled 'Get out of the car!' he said in his statement.
Another officer reached over and opened the front passenger door.
"I re-holstered my firearm and dragged Gargasoulas from the car with a number of other police members," he said.
He was handcuffed and had been shot at and tasered.
Earlier that day, Sen Const Diwell had followed the offender Melbourne's inner west in a police vehicle and almost met his car head on but it was decided the move was too dangerous.
"We became aware the suspect vehicle was heading straight towards us and we would meet the vehicle head on within seconds," he said in his statement.
"We conducted an assessment of the situation and decided such a confrontation posed an unacceptable risk to ourselves as well as the public."
As other police vehicles tailed the offender, Sen Const Diwell's vehicle lost sight of him.
They heard via police radio he had made his way to the city and was driving down tram tracks on Flinders Street and doing donuts outside the train station.
By that time, the risks to the public had increased and there were concerns Gargasoulas may hurt pedestrians as he accelerated up to 80km along tram tracks with police in tow, the detective said.
He eventually mowed down and killed six people and injured dozens more.
Gargasoulas, who suffers paranoid schizophrenia, was jailed in February for at least 46 years in what was described by the sentencing judge as one of Australia's worst examples of mass murder.
The inquest before coroner Jacqui Hawkins continues on Monday.