The victim's nephew Wallyson de Jesus told Metropoles that his uncle had been riding a motorcycle when he was stopped. He said he tried to tell the officers that his uncle suffered from mental illness.
"They asked him to raise his hands and found medication packets in his pocket," Wallyson said. "My uncle got nervous and asked what he had done. I asked him to calm down and listen to me."
The harrowing footage shows the two uniformed officers pinning the man to the ground, kneeling on him.
It then cuts to them trapping the man inside the trunk of their patrol car, holding the door closed as just his legs protrude, thick white smoke spilling out from inside the vehicle.
The legs can be seen kicking, frantically at first, then subdued... until they go completely still.
The officers then open the trunk and push the man's motionless body further into the car.
"They threw a type of gas inside the suitcase, went to the police station, but my uncle was unconscious," his nephew said. "In view of that, the police took him to the hospital, but it was too late."
In a statement to the outlet, the Polícia Rodoviária Federal (Brazilian Federal Highway Police) said the man had "actively resisted" arrest, so they used "immobilization techniques" and non-lethal instruments to subdue him, "due to his aggressiveness."
They said that en route to the police station, the subject fell ill so they diverted toJosé Nailson Moura hospital where he was treated, but later died.
The incident is under investigation to see whether any disciplinary action for the officers is required.
Genivaldo's widow, Maria Fabiana dos Santos, told Globo the officers "acted with cruelty to kill".