New video footage shows George Floyd in a struggle with police in the moments leading up to his death.
Though Mr Floyd, 46, cannot be seen in the clip, one officer is seen struggling with him on the backseat of the police car.
Shaun King, an activist campaigning for justice for Mr Floyd, posted the surveillance footage on Instagram.
He wrote: “BREAKING: Just got this new video. It’s all coming together. Police were in the car beating the sh** out of George Floyd. One stands watch, while the others attacked him.”
Derek Chauvin, who knelt on Mr Floyd’s neck for over eight minutes in Minneapolis, has been charged with murder. Three more police officers who were responsible for his care in custody have been sacked.
The three police officers witnessed Mr Floyd’s death and stood guard as officer Chauvin employed a chokehold as Mr Floyd pleaded he was unable to breathe.
Mr King, who launched a grassroots law project, described the victim as a peace activist and respected community leader.
Mr Floyd had moved from his hometown Houston to Minneapolis in search of better career opportunities for himself and his family, Mr King wrote.
He added: “He started driving trucks in Minnesota and went on to also work at a restaurant in Minneapolis as a security guard. He was known in his new job as a hardworking and friendly employee. Everywhere he went he was the same caring and kind spirit.”
The campaign is calling for all of the officers responsible to be tried and charged.
His death has reignited anger over police killings of black Americans and sparked renewed calls for an end to police brutality.
Dozens of US cities are facing their fifth night of unrest as protestors calling for justice clash with police.
On Saturday, a sheriff in Michigan joined demonstrators to ‘help them have a voice’ as he joined their protest. Chris Swanson assured protestors: “The only reason we’re here is to make sure you have a voice, that’s it’ said Chris Swanson. ‘I want to make this a parade, not a protest.”
The sentencing of officer Chauvin, who was charged with third-degree murder, has had a lukewarm response. Lawyer Benjamin Crump told CBS news he should have been charged with first-degree murder.
“The fact that officer Chauvin kept his knee on his neck for almost three minutes after he was unconscious. We don’t understand how that was not first degree murder. We don’t understand how all these officers haven’t been arrested,” he said.
Multiple US states have imposed a curfew in a bid to control the riots.