Phillips, a frequent Guardian contributor, and Pereira had encountered Native Americans close to the Javari Valley Indigenous Territory's entrance.
Authorities discovered their dead in the jungle thanks to the assistance of the local Indigenous population after their disappearance sparked a significant international uproar.
According to the statement, they have admitted to the crime, and witness accounts suggest Oseney da Costa de Oliveira also took part.
The three are all locals, and Pereira requested that Phillips take their photo when they went by in a boat, claim the prosecutors.
The prosecution also stated that they believed this motive to be "frivolous," a label that can result in harsher punishments under Brazilian law.
The prosecution added that they considered this purpose to be "frivolous," a term that, in accordance with Brazilian law, carries higher penalties.
He was armed and had left the government agency for Indigenous affairs to train local Indigenous people in the patrolling of their territory
Pereira was delivering this evidence to the Atalaia do Norte authorities on the day they were killed.