Three months out of training, a junior policeman made the toughest call during the Bourke St attack.

He’s the man who put an end to the devastating act of terror on Friday – but just three months out of the academy, the police officer who shot Bourke Street attacker Hassan Khalif Shire Ali has had a harrowing introduction to the police force.

It was like any other Friday afternoon in Melbourne when 30-year-old Ali pulled up in Bourke Street in his four-wheel drive.

But things took a terrifying turn when Ali jumped out of his car – which he had attempted to explode – and stabbed three men including beloved 74-year-old restauranteur Sisto Malaspina, who died at the scene.

Incredible acts of bravery unfolded as civilians – including a courageous homeless man wielding a trolley who has captured the attention of the nation, and another bystander with a chair, tried to overpower the attacker.

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But it was a new police officer who pointed his gun squeezed the trigger – shooting him in the chest and ending the horrific ordeal.

The act was captured on phone footage by witnesses – a moment which will no doubt stick with the new policeman for the entirety of his career.

Ali – who it has been confirmed was suffering mental health and substance abuse problems before the attack – later died in hospital.

Speaking to media after the incident, Chief Commissioner Graham Ashton was full of praise for both the officer and another junior policeman.

“These members found themselves in a dangerous situation very quickly,” Mr Ashton said.

“They acted very bravely. They endeavoured to do their job and they did that pretty effectively and bravely. They followed their training really well (and) I’m proud of their efforts.”

Mr Ashton said police were trained to kill if they saw a threat to the lives of the public or fellow officers.

“We don’t train people to wound people with firearms,” he said.

“You’re trained to shoot to kill, not to shoot to wound.”

In the wake of the attack, he said both junior officers were “in good spirits although shaken up”.

As reported by The Age  friends of Ali’s family have revealed that he had grown increasingly “delusional” in the weeks before his rampage on the city.

Isse Musse told the newspaper Ali was “complaining he was being chased by unseen people with spears”.

Another source said his life had “spun out of control”, adding that he had been kicked out of the family home several times.

The Sunday Herald Sun also reports that he had recently split from his wife.