A mental health crisis line social worker's response to a plea for help from a suicidal young man killed hours later by police was "not satisfactory", a coroner has found.
Kobee Huddy, 20, was brandishing a large knife and advancing on a police officer when he was fatally shot in Seaton, in Adelaide's western suburbs, in May 2019.
Deputy SA Coroner Ian White released his findings into the fatal shooting on Friday.
Mr Huddy, who had borderline personality disorder, had more than 25 interactions with the health system for suicide attempts in the two years before his death, often linked to binge drinking and drug use.
He called the mental health triage service seeking help on May 25, 2019.
The social worker he spoke to faced "stern criticism" at the inquest from police, a psychiatrist who reviewed the call and Mr Huddy's mother, Belinda Huddy, for her "dismissive and abrupt" phone manner, Mr White said.
"I believe that (the social worker's) conduct of this call was not satisfactory," he said.
In a subsequent call to triple zero, Mr Huddy was aggressive and threatening, stating he had a gun and demanding that police "send me some cops for bloodshed".
Police confirmed his location at his girlfriend's house and sent officers to detain him but he left the home in a car with people who were taking him to hospital.
When Sgt Darren Mead stopped the car, "the knife was produced after Sgt Mead ordered Kobee to kneel", Mr White said.
"Kobee refused and advanced on him as Sgt Mead was retreating with the gun now drawn."
Sgt Mead told other officers he "continued to walk backwards but by the third step, he was at a point where I believed I couldn't avoid the knife".
He fired a shot that struck Mr Huddy in the chest.
Mr Huddy later died in hospital.
Mr White found Sgt Mead's discharge of his gun was legally justified as self-defence.
Major Crime detectives initially believed Mr Huddy intended to "provoke a lethal response from a law enforcement officer" but later concluded his actions in his final hours were "inconsistent with such an intention".
"Kobee said 'I'm sorry' to the SAPOL officers who immediately assisted him after he fell," Mr White said.
"Those final words showed his true nature underneath all the difficult problems BPD, drugs and alcohol had caused him."
Sgt Mead's mental health suffered and progressively worsened in the next four years, and he was diagnosed with complex post traumatic stress disorder.
He died of natural causes in 2023 aged 49.
Mr White said he was a "caring and dedicated officer".
Mr White made no recommendations, noting that SA Police were trialling mental health nurses accompanying police patrols and encouraged them to further develop the strategy.
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