For Professor Gracelyn Smallwood, a late-night phone call about another Aboriginal man being shot and killed by police was the final straw.
Aubrey Donahue, 27, died after being shot four times by police, who say he advanced on officers while armed with a knife in Mareeba, west of Cairns, on Saturday.
Coroner Terry Ryan will hold an inquest into the shooting but police have already revealed there is no close-range footage of the incident.
On Wednesday, Prof Smallwood resigned from the Queensland Police Service First Nations advisory group.
"Half an hour after the shooting happened I got a call from a family member describing how four bullets were put in the young man's abdomen," she told AAP.
"I sent (Police Commissioner Katarina Carroll) a text at midnight on Saturday and said, 'What's going on? People are saying he was unarmed. Why was he shot four times in the abdomen? Why didn't they shoot him in the kneecaps to bring him down?'.
"Because what the community was saying to me on the phone is that it was a welfare check and that he was trying to self-harm."
Prof Smallwood said that she understood police procedure in Australia was to shoot to kill if officers believed someone was armed and they felt threatened.
"You've got three or four police officers with ammunition in heavy guns pointing at the victim," she said.
"Maybe he's got a knife - but he hasn't got a knife like Crocodile Dundee and he doesn't have a machine gun.
"They didn't have their cameras on and they felt intimidated, so they just put four bullet holes in this boy's abdomen and killed him."
Gracelyn Smallwood is a retired professor of nursing and midwifery and has been an Indigenous activist for decades, including with the campaign for justice for Mulrunji Doomadgee.
Mr Doomadgee died in custody in Palm Island from massive internal injuries.
Prof Smallwood has also been advocating for changes in the way police restrain people, particularly in the wake of the death of Townsville Indigenous man Noomba in 2018.
She joined the advisory group because she believed she could help change things for the better from the inside.
Prof Smallwood said she believed in the cultural changes Ms Carroll was trying to make.
"I'm optimistic that it is going to change but, as a hardcore activist, I felt that they were taking their time with the stranglehold laws," she said.
"The shooting in Mareeba was the last straw. I can't sit here as a hardcore activist and not do something.
"And the only thing I thought of doing was resigning and making a statement.
"It wasn't about me. It was about a lot of injustice that's happening to our people all around Australia."
In her resignation letter, Prof Smallwood calls for changes in police procedures and for governments to work with Indigenous communities to reduce the number of children in out of home care and the criminal justice system.
Ms Carroll said in a statement that she was disappointed that Prof Smallwood had resigned from the First Nations Advisory Group but she understood her reasons.
She said she remained committed to working with the group to improve policing practices with Indigenous people in Queensland.
"While I acknowledge this is a difficult time for the First Nations Advisory Group members and First Nations communities in Queensland, I am encouraged by the recent progress we have made as a group and look forward to continuing to enhance relationships with members for the benefit of the community," Ms Carroll said.
