The commissioner of the Northern Territory’s Independent Commission Against Corruption (Icac) Ken Fleming QC will step down from his role overseeing the investigation into the police shooting death of Indigenous teenager Kumanjayi Walker.

Fleming had faced criticism that he could not approach the investigation impartially after saying at a protest rally in Alice Springs: “One of the most important messages today is ‘Black Lives Matter’. Anybody who says contrary to that is guilty of corrupt behaviour.”

Fleming released a statement on Tuesday, saying he had informed the NT’s chief minister Michael Gunner of his decision to recuse himself from the investigation, out of a concern over an apprehension of bias.

Fleming said his decision to step aside followed advice from Icac inspector Bruce McClintock SC, who would now receive any complaints about the case.

“My intention when participating in the community meetings in Central Australia was to explain our ability to independently look into these matters to the communities who are upset and seeking the truth,” Fleming’s statement said.

“I accept that some of my comments have led to the perception among some observers that I am closer to one side than another on this matter, and so I will no longer be involved in it.

“The public must trust in the Icac’s ability to provide independent oversight of public bodies and public officers.”

Former NT attorney-general Daryl Manzie led the criticism of Fleming, arguing the comments had created a clear perception of bias.

“I think anyone looking at this independently would say ‘how can this man be independent’ and seen to be independent, which is more important, because it’s the perception that really counts,” Manzie, the Country Liberal Party vice-president and a former police officer, said.

Nineteen-year-old Kumanjayi Walker died after he was shot at Yuendumu, 300km from Alice Springs, on the night of Saturday 9 November, when two police officers attempted to arrest him for breaches of his suspended sentence.

NT police constable Zachary Rolfe, 28, has been charged with one count of murder.

But beyond the charge against the policeman, serious concerns have been raised about the way police and health officials dealt with the shooting, including their treatment of Walker’s relatives, who were left waiting for hours outside the police station seeking answers about his condition.

Walker died inside the police station from his injuries but did not receive critical emergency care, and his family were not notified until hours after his death.

NT health officials left Yuendumu in the hours before the police shooting, saying staff had “raised safety concerns” that morning after “community unrest”.

The Medical Retrieval and Consultation Care Centre, which handles medical emergencies across central Australia, provided clinical advice to police at the time of the shooting but did not immediately call for an airlift.

Walker had died by the time staff from the nearby Yuelamu health centre arrived at the station.

Walker is the second Aboriginal person to die after being shot by police in the past two months. In September, 29-year-old Joyce Clarke, a Yamatji woman, was shot outside a house in Geraldton and died in hospital.