In video purportedly showing the incident on Wednesday, two federal highway police officers are seen attempting to restrain 38 year-old Genivaldo de Jesus Santos on the ground.
The footage in the widely-shared video is edited, leaving gaps where it is unclear what happened between the clips.
The next clip shows officers allegedly putting Santos in the trunk of a Federal Highway Police patrol SUV. The individual appears to push back against the officers’ efforts to get them entirely into the car.
In another clip, officers are shown using the trunk of the police car to pin down the man’s legs while the vehicle fills with an unknown white smoke or gas. The trapped man is heard screaming. In another clip, the police officers are seen holding the man’s legs down while the gas dissipates, and after about a minute and a half, his legs appear to stop moving. The officers are seen holding the trunk of the vehicle closed.
Federal Highway Police from the state of Sergipe said in a statement that Santos “actively resisted” the officer’s approach with “aggressiveness” and the police officers had to use “immobilization techniques and instruments of lower offensive potential” to contain him.
The police say the man “fell ill” while being transported back to the station and later died in the hospital.
The Sergipe’s coroner’s office (IML) said in a statement that Santos died of asphyxiation but said “it was not possible to establish the immediate cause” of it. IML said it would conduct further exams to establish “how the asphyxia process took place.”
Police have opened an internal investigation into the case.
CNN has reached out to the police for comment on the incident and why the man was stopped.