Constable Zachary Rolfe shot Kumanjayi Walker, 19, three times during a bungled arrest in Yuendumu, northwest of Alice Springs, on November 9, 2019.
An inquest into his death heard on Thursday that Const Rolfe held a "debrief" barbecue for colleagues at his home two days after the incident.
During the evening, Constable James Kirstenfeldt, who was part of the Yuendumu arrest team, texted Const Rolfe and warned him to stop talking about the shooting.
"Stop talking to these c***s," he said in a bid to help his friend.
"Don't trust these snake c***s ... They are covering their own arse.
"You left and and didn't get to see the aftermath of the arse covering," he wrote in another, in reference to Const Rolfe being evacuated from Yuendumu before the other four members of the arrest team.
"Lawyer, lawyer, lawyer ... Don't trust these snake f***s, lawyer told you not to comment," Const Kirstenfeldt said to remind his mate about the legal advice he'd received.
Asked by counsel assisting Peggy Dwyer to explain the texts and who the people "covering their own arse" were, Const Kirstenfeldt said he didn't know.
But he agreed he texted Const Rolfe because he didn't want some of the people at the barbecue to know what he was saying and he was concerned for his friend.
"My sentiment of this is of being the lowest rank of the whole incident and ... the old expression of 'it rolls downhill'," Const Kirstenfeldt said.
"It was probably going to be all the people of the lower ranks thrown under the bus."
Dr Dwyer reminded Const Kirstenfeldt that the quality of his evidence would impact his credibility.
The inquest heard some of the officers involved in the shooting were at the gathering, along with senior and junior police from Const Rolfe's Alice Springs patrol group.
Some of them allegedly discussed police use of force and their training when confronted by an offender armed with an edged weapon, as Mr Walker had been when he was shot.
It was decided that Const Rolfe had followed his training and would be back on the job soon.
He was charged with Mr Walker's murder two days later and acquitted at trial in March.
The officers' conversation at the barbecue is among 54 issues related to Mr Walker's death that Coroner Elisabeth Armitage is exploring amid concerns it may have contaminated Const Rolfe's evidence at his trial.
Const Kirstenfeldt told the coroner he spoke to his own lawyer after Const Rolfe was arrested and was told he was also likely to be arrested, despite not being directly involved in the shooting.
"I sat at home for a month waiting for that to occur or hear from it or to be told 'no' or anything. It didn't happen," he said.
The inquest heard the arrest team was ordered by a senior officer at Yuendumu police station to take Mr Walker into custody at 5am, when he was likely to be sleepy and compliant.
Instead, the men started searching for him after leaving the police station at 7.06pm and Const Rolfe shot him inside his grandmother's home 15 minutes later.
Asked how the 5am arrest plan came to be abandoned, Const Kirstenfeldt said: "I have thought about it and thought about it and I ... it's just not in my memory".
He told the coroner he remembered it being discussed at the police station, but denied being handed a printed version of it despite CCTV footage showing him holding a document in the minutes before the men started searching for Mr Walker.
The hearing continues on Friday.
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