Belgium's director-general of police has said he is deeply moved by a video showing a Slovak man being pinned down in a cell hours before he died.
André Desenfants said he was temporarily stepping back from his role as number two in the federal police.
Jozef Chovanec was arrested at Charleroi airport in 2018 after causing a disturbance on a plane.
His widow has said she wants to know why they treated him in that way, and has called for a new inquiry.
In the graphic video, Chovanec is seen banging his head against the wall of his cell and eventually bleeding. Officers then forcibly restrain him.
A female officer appears to make a Hitler salute while laughing and a male officer is seen sitting on the man's chest for 16 minutes.
Chovanec, 38, died of a cardiac arrest in hospital the following day.
'Worse than an animal'
The video was released by his widow, Henrieta Chovancova, after she became frustrated with a two-year inquiry that police said had been delayed by the coronavirus pandemic.
"Why did they treat him like this? Worse than even an animal, like he wasn't even a human being," she told Belgium's VRT News.
She told Het Laatste Nieuws; "After the videos of the arrest of the American George Floyd, I immediately thought, 'my husband died the same way', except that police also laughed out loud at my husband and a policewoman next to him did a Hitler salute."
Chovanec was originally detained when he forced his way on to the plane because he could not find his boarding pass.
What have police said?
The original police inquiry into his death has dragged on and Mr Desenfants said although he was personally responsible for airport policing he was unaware of the images. But said he could not "accept nor tolerate" them.
He had decided to step aside because he felt unable to fulfil his role for the time being.
A lawyer for the policewoman told Het Laatste Nieuws that she was interviewed by the police inquiry in May 2018 and was asked about the video.
"She was embarrassed but it was a kind of knee-jerk reaction," François Feron told the paper. "Because she heard Jozef Chovanec making accusations - she assumes in German or a Slavic language - at the time and in that context she thought a Hitler salute was funny. Wrongly, of course, but she realises that too."
Philippe Hensmans of Amnesty International called for a thorough investigation, saying the incomplete images showed someone inflicting blows on himself and in need of help.
Chovanec's family said they did not know the reason for his erratic behaviour during police custody, and a post-mortem examination had shown he was not under the influence of drugs or alcohol.
Amnesty said the incident was also a reminder of the 2010 death in custody of Jonathan Jacob. An inquiry began into his death only when images were broadcast on TV three years later, the rights group said.
A spokesperson for the Charleroi public prosecutor's office said all officers involved in the incident had been interviewed, but added that "due to the crisis surrounding Covid-19, there has been a delay".