Arizona Tribune - Photo triggered Amazon murders of journalist, guide: AG

Pereira had asked Phillips to photograph the boat, according to a statement from the office that said this detail may count as an aggravating factor in sentencing.

The details were revealed after the filing Thursday of charges against the three men suspected of committing the double murder.

Amarildo da Costa de Oliveira and Jefferson da Silva Lima have both confessed to the crime, according to officials, while Oseney da Costa de Oliveira -- brother of Amarildo -- has not.

The trio stands accused of murder in the first degree and of hiding the bodies.

"Bruno was killed by three bullets, one in the back without any possibility of defense," said the statement.

"Dom was killed simply because he was with Bruno, in order to ensure impunity for the previous crime."

Phillips, 57, and Pereira, 41, were shot dead while returning from an expedition in a remote region of the rainforest that is plagued by drug trafficking, illegal gold mining and fishing.

Phillips, the author of dozens of articles on the Amazon and a long-time contributor to The Guardian newspaper and other major news organizations, was traveling to the Javari Valley as part of research for a book.

Pereira was serving as his guide, and had previously traveled with him to the area.

An outspoken defender of Indigenous rights, Pereira had received multiple death threats prior to his murder.

Police are investigating a possible link to illegal fishing on protected Indigenous lands -- an issue close to Pereira's heart -- as a motive for the killing.

N.Walker--AT