A Wadeye man who died after police prevented him from boarding a flight was a senior Wadeye Elder who lobbied for bilingual schooling and better education funding for his community.
A death-in-custody investigation is under way after federal police stopped the 68-year-old from joining a flight out of Darwin on May 30, on reports he was intoxicated.
He was taken into "protective custody" but on arrival at Royal Darwin Hospital he was found to be unconscious, prompting medical staff to commence CPR, with resuscitation efforts proving successful.
He was transferred to the intensive care unit for ongoing treatment for a suspected medical event but died there on Saturday.
"The cause of the man's death remains undetermined pending a postmortem," Northern Territory police have said.
"The incident is being investigated as a death in custody as the man was in the custody of the AFP at the time of him first losing consciousness."
The AFP has said the man was not arrested and was "not restrained at any point by AFP officers".
Aboriginal leaders from the Top End's Daly region have expressed their communities' grief over the loss of the Elder.
Thamarrurr Development Corporation representing Wangga, Lirrga, Wulthirri and Tharnpa peoples said in a social media post that he was a "much loved and respected senior man, who was a mentor to us all".
"A great visionary and educator, a campaigner for a better life for his community and a respected leader, he will be greatly missed."
The Elder was a champion for bilingual education and had produced children's books in local tribal language.
In 2007 he took part in a racial discrimination action in the Human Rights and Equal Opportunity Commission arguing Wadeye children received less than half the school funding received by other NT children.
Then-federal education minister Peter Garrett announced the community would get a $7.7 million funding package in exchange for dropping its complaint.
Northern Land Council chair Matthew Ryan said the Elder, who had been a council member, was a "quiet achiever" whose legacy would live on.
"My heart goes out to his loved ones and all mob across the Wadeye and Darwin Daly regions," he said on social media.
Opposition leader Selena Uibo said the Elder's loss would be "be felt deeply across the territory".
"He was a respected and strong leader - valued for the guidance he provided to those he worked alongside and the outcomes he helped deliver for his community," Ms Uibo said.
NT Chief Minister Lia Finocchiaro said her government recognised the "pain and grief being felt" and her thoughts were with the man's family and loved ones.
Catholic Bishop of Darwin Charles Gauci said he had known the Elder for many years and he was "deeply saddened at his death".
"I was able to accompany him on the last day of his life, I was in the hospital with his wife and family and to pray with him and to be there with them, walking with them at this very significant time," he told the ABC.
"He believed in education as empowerment and he was an educator for many years himself.
"He was co-principal at the school at Wadeye and really contributed deeply and widely there for the education of young people."
NT Police will prepare a report for the coroner.
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