Pereira worked for a period at the National Institute of Social Security [pt] (INSS) in Recife.[6] After getting a job in the environmental program at the Balbina Hydroelectric Power Plant, Pereira went to the Amazon region.[5]
After a few years at the Balbina hydroelectric plant, Pereira was approved in a competitive examination by the National Indian Foundation (Funai) and chose to go to the Javari Valley, the indigenous land with the highest concentration of isolated indigenous people in the world. In 2018, Pereira became the general coordinator of Isolated and Newly Contacted Indigenous People at Funai, when he headed the largest expedition for contact with isolated groups.[5]
In 2019, Pereira led the largest expedition to contact isolated indigenous people in the last 20 years. However, after pressure from ruralist sectors linked to the Jair Bolsonaro government, he was removed from his post in October of that year by Sérgio Moro then executive secretary at the Ministry of Justice, Luiz Pontel.[2][7][8]
According to indigenous entities, Pereira was constantly threatened by miners, loggers, and fishermen.[2][7][9]
Pereira also coordinated a project to equip indigenous people to defend their territory with drones, computers and training. Pereira claimed that the invaders felt more at ease as a result of the permissiveness of the public authorities, and surveillance has undergone a continuous weakening process.[10]