None of the four police officers involved in the shooting death of an armed man at Sydney's busiest train station had a Taser at the time, an inquest has been told.

Danukul "Dan" Mokmool, 30, was shot in the head and died after he held up a florist with a broken bottle and then ran at police on the Eddy Ave concourse at Central station on 26 July in 2017.

About 6.45pm - as stunned commuters filmed on their phones - Mr Mokmool charged rapidly at Senior Constable Frederick Tse shouting "I'm going to kill you, I'm going to kill you", counsel assisting Adrian Williams told the NSW Coroners Court on Monday.

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The plain-clothed policeman stepped back before firing three shots. Another officer, Sen Const Jakob Harrison, also fired once.

The officers and two colleagues had arrived less than a minute earlier. They'd formed a semi-circle around the entrance of the florist, drawn their guns, and demanded Mr Mokmool drop his weapon.

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Inside, with scissors in both hands and more down his pants, Mr Mokmool screamed: "I'm not giving up. Shoot me. Shoot me dead. Just f***ing kill me."

"The timeframe was very short indeed," Mr Williams said, adding an officer with a Taser arrived at the scene shortly after the shooting.

Capsicum spray was used moments before the shooting but no effect was observed.

Whether Mr Mokmool was suffering from a mental health illness immediately prior to his death, and whether police had alternatives to lethal force, are among the issues being examined at the inquest.

Mr Williams said the deceased had left high school aged 15 and had spent time in custody. He had a history of using drugs including cannabis, methamphetamine and heroin.

However, an expert is expected to testify only one drug - methadone - was found in Mr Mokmool's system after his death and it had no relationship to his behaviour on the night.

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Mr Williams said Mr Mokmool appeared well the day before the shooting but his mental state had deteriorated by the afternoon of July 26.

Mr Mokmool asked his brother "Why do you want to kill me?" before later calling triple zero to say he feared for his life and people were trying to "chop me up and kill me".

By the time police arrived at Mr Mokmool's Heckenberg home to check on his welfare at 6.30pm, he was already travelling by train to the city.

Deputy state coroner Elaine Truscott is expected to be told how NSW Police has responded to recommendations from two previous inquests into fatal police shootings.

The force in 2018 was advised to teach dispatchers and officers how to better recognise when people were suffering from a mental health crisis and how to de-escalate the situation.

The inquest continues.

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