A forwarded message circulating in northern Brazil warned people to stay inside on the night of Nov. 4 when 10 people were killed.

The message was circulated on a popular messaging mobile app, WhatsApp, and began circulating after the death of the police officer, BBC reported.

On Tuesday evening, as eyes in the U.S. were glued to election results, Brazilians in Belem were looking at their phone screens reading the unusual message, which was circulating both as a text and audio clip.

"Don't go to Guama, Canudos or Terra Firme tonight. It concerns your security. One of our policemen was killed and we will be cleaning the area. There's no stopping any of us, not even the highest colonel. The boys are on the loose. Please stay at home. Don't go hanging out on street corners," the clip said, according to BBC.

The message was allegedly sent by renegade officers, though not an official public service announcement from the police department, seeking revenge for Antonio Marcos da Silva Figueiredo.

And the origin of the message has not been traced.

Witnesses told BBC they saw the alleged killers riding motorcycles during the six-hour spree, which resulted in 10 deathsthat night.

Soon after, photos of what appear to be dead bodies in the streets were shared.

Camilla Costa, a BBC journalist based in Sao Paulo, said this isn't the first time a killing spree like this has happened.

Earlier this year, a policeman was shot in Campinas, who was avenged by police officers who killed 12 people, Costa said.

It has not been determined if the motorcycle killers were police officers, but tensions in the area remain high, and schools and universities were closed the day after.

Police in Brazil have recently been investigating criminal gangs who use WhatsApp to circulate similar curfews. Usually the app is used when there is a confrontation with another gang or, as the police expected, to negotiate drug sales.