A search in the deep Brazilian Amazon for missing British journalist Dom Phillips and Indigenous rights expert Bruno Araujo Pereira has now turned into a homicide investigation, Brazilian federal police confirmed to ABC News.
In a news conference Wednesday night in Manaus, the capital of the Amazonas state, Federal Police Chief Alexandre Fontes confirmed that the main suspect -- Amarildo da Costa Oliveira, also known as "Pelado" -- confessed to police that he fatally shot Phillips, 57, and Pereira, 41, June 5.
According to the police, Oseney da Costa Oliveira, Pelado's brother, denied any involvement in the double slaying, claiming he stayed home on June 5 and went out hunting the following day. Police said he was arrested for aggravated murder and will remain in custody, police said.
Fontes said Pelado da Costa Oliveira purportedly confessed to the killings on Tuesday and showed police the location of the bodies. He also said the suspect told investigators the whereabouts of a boat Phillips and Pereira were traveling on.
The latest developments come after human remains were found on Friday in the remote Javari Valley region of Brazil, near the border with Peru. Police told ABC News on Wednesday that forensic exams are still being conducted on the remains to "fully" determine if they are Phillips and Pereira.
Phillips' wife, Alessandra Sampaio, told ABC News that police have informed her that the two bodies recovered from the Javari Valley are likely those of her husband and Pereira.
The men went missing on June 5 while on a boat trip on the Amazon as part of a reporting project Phillips is working on.
The brothers came under suspicion and were detained after human blood was found on their fishing boat. Police are testing the blood to see if it matches either Phillips or Pereira.
Witnesses told police the brothers' boat was seen traveling behind one Phillips and Pereira were on around the time they disappeared, Brazilian authorities said.
At least five other people have been questioned since the investigation started and police said Wednesday that more arrests are possible.
A motive for the slayings remains under investigation.
Phillips, 57, and Pereira, 41, were last heard from by colleagues while traveling by boat in the Javari Valley region of the Amazon, relatives said.
Phillips was doing research on patrol teams Bruno Pereira had helped create to crack down on illegal fishing and hunting, an initiative that prompted threats against Bruno Pereira, The New York Times reported on Tuesday.
Phillips was on one of his last reporting trips for an upcoming book he was writing as part of a 2021 fellowship awarded by the Alicia Patterson Foundation, according to Margaret Engel, the foundation's executive director.
There was an international outcry after accusations surfaced that responding agencies were slow to act in investigating the disappearances.
At a vigil outside the Brazilian embassy in London last Thursday, Phillips' family members urged Brazilian authorities to keep investigating.
"We want to find out what is happening to them and we want anyone responsible for any criminal acts to be brought to justice," Phillips' sister, Sian Phillips, said. "We want a persistent, deep and open investigation."
The family's calls were joined by environmentalist groups, activists, celebrities and news organizations.
Brazilian President Jair Bolsonaro initially appeared to cast blame on Phillips and Bruno Pereira, saying they "were on an adventure that is not recommended." He continued, "It could be an accident, it could be that they were executed, anything could have happened."
Those comments were "obviously upsetting" to the family said Paul Sherwood, Sian Phillips' partner.
People close to Phillips and Pereira refuted that they were on a reckless excursion. Engel, who was collaborating with Phillips on his upcoming book, said, "Nothing he did was off-the-cuff."
"He was not naïve about the dangers that were there," she said.
Soraya Zaiden, who worked closely with Pereira at the Union of Indigenous Peoples of the Javari Valley (Univaja), a local organization assisting in the search for the missing men, said Pereira was unlikely to put anyone in danger.
Violence has taken place in the past in the Javari Valley, where illegal mining activities, drug trafficking and deforestation is resisted by groups trying to preserve the rainforest and the culture of its Indigenous inhabitants. A member of the Brazilian government agency FUNAI, which is tasked with protecting Indigenous peoples' interests, was shot and killed in the Javari Valley in 2019, advocates told ABC News.
ABC News' Matt D. Allen contributed to this report.