Police can be heard on radio warning “someone needs to take this vehicle out before he kills someone” moments before pedestrians were run down in Melbourne’s Bourke Street.

The horror of the 20 January 2017 carnage that killed six people and injured dozens more was heard in the police radio played during the first day of an inquest into the rampage.

“This car is a danger to pedestrians and is in the middle of the Flinders and Swanson street doing donuts,” one officer warns.

Police add the driver is armed with a knife, having just stabbed his brother, and very dangerous.

Seconds later, a frantic voice adds: “Someone needs to take this vehicle out before he kills someone.”

In the seconds that follow, police report: “We have someone down on – multiple victims. Many units as involved as you can. We need to take him out.”

James Gargasoulas was tailed by police for hours before driving a stolen car through the CBD and mowing down dozens of pedestrians. He was eventually shot and tasered after his car came to a halt.

Bourke Street killer James Gargasoulas was jailed for life for the 2017 massacre. Photograph: Penny Stephens/AAP

Police transmissions detail attempts to catch the man they described as being in “maniacal psychotic state” and threatening to kill people.

During that time, he sped and drove erratically and evaded police.

He texted an officer who was trying to negotiate a peaceful arrest that he was “the saviour” and would not surrender.

The counsel assisting the coroner, Stephen O’Meara QC, said the police pursuit policy at the time would be examined during the inquest.

“This inquest will attempt to distill from this tragedy lessons that may save lives in future,” he said.

The coroner said she was astounded more people weren’t killed.

“The number of people affected by the actions of the offender is vast,” Jacqui Hawkins said.

Hawkins paid tribute to the victims. “I acknowledge all those affected by the tragedy and their enduring physical and psychological pain,” she said.

“One by one these lives were extinguished. These six individuals were going about their day in peace. The murderous actions of the offender ended their lives.

“The events were surreal. It’s a day that’s forever etched in our minds.”

The victims included three-month-old Zachary Bryant and 10-year-old Thalia Hakin along with Jess Mudie, 22, Yosuke Kanno, 25, Matthew Si, 33, and Bhavita Patel, 33.

Hawkins said it was her duty to give these victims a voice and ensure lessons were learned from the circumstances of their deaths.

Family members of the victims were expected to address the court later on Monday.

Gargasoulas’s release from custody during an out-of-sessions bail hearing, six days before the massacre, is being investigated during the hearings.

Gargasoulas, who suffers paranoid schizophrenia, was jailed in February for at least 46 years for what was described by the sentencing judge as one of Australia’s worst examples of mass murder.