Brazilian police on Tuesday arrested the supervisor of a Carrefour supermarket in Porto Alegre where security guards beat a black man to death, and accused her of collaborating with the killers.

Protesters demonstrate on Sunday at Carrefour supermarkets across Brazil after the death of a Black customer who was beaten by two private security guards. Photo: VCG

Supervisor Adriana Alves Dutra had the authority to stop the guards from beating 40-year-old Joao Alberto Silveira Freitas on November 19, said homicide investigator Vanessa Pitrez with the Civilian Police.

"She had authority over the two guards," and because of that "the law sees her as a homicide co-conspirator," Pitrez said at a press conference, as cited by the news site UOL.

Pitrez has asked that the woman be temporarily jailed.

Alves Dutra appears in a video that went viral standing by as Silveira Freitas is punched in the face and head in the supermarket parking lot by one security guard as the second guard restrains him.

According to the preliminary investigation Silveira Freitas was beaten for more than five minutes before being immobilized by his attackers and dying of asphyxiation. Both security guards have been arrested.

Dutra apparently lied to police in her initial account.