RIO DE JANEIRO — Paulo Paulino Guajajara knew that a violent death could come his way.

Three of his fellow “guardians of the forest” — a squad of armed indigenous sentinels — had already been killed by land grabbers trying to knock down and develop one of the last remaining shards of the Amazon rainforest in Maranhao state. Paulino would talk about this fear frequently, then swallow it down and head out on another patrol.

On Friday, his worries were realized. State authorities say Paulino and another guardian from the Guajajara tribe were out fetching water when at least five armed men surrounded them and opened fire. Paulino, 26, was shot in the neck. He died in the forest.

As deforestation in the Amazon surges under Brazilian President Jair Bolsonaro, threatening thousands of indigenous people, Paulino’s death has drawn media attention and promises by officials to act.

The governor of Maranhao announced the creation of a task force to protect indigenous life, and Justice Minister Sérgio Moro vowed “to bring those responsible for this serious crime to justice.”

The contest for land along the Amazon frontier, which pits ranchers, land grabbers and the indigenous against one another, has always been bloody. But as enforcement of environmental regulations slackens and deforestation rises under Bolsonaro, there’s fear that the recent deaths of the forest guardians might be only the beginning.

In the first eight months of Bolsonaro’s tenure this year, authorities issued the fewest fines for deforestation infractions in at least two decades, Human Rights Watch reported. Deforestation over that period was more than double that of the previous year. An expanse larger than Delaware has been lost this year alone.

The retreat of the federal state and the encroachment of developers have placed more pressure on nontraditional defenders of the forest — small-time farmers, cops, indigenous tribes — viewed by many conservationists as crucial to maintaining its structural integrity.

But their work is increasingly subject to threats and violence. More than 300 people have been killed in the past decade while trying to protect the land, according to the nongovernmental Pastoral Land Commission — and that figure, analysts say, is probably an undercount. In a frontier as vast as the Amazon, where police have few resources and where many killings happen in remote areas, many deaths receive little notice.

“Some of the investigations were so bad and didn’t do basic things like an autopsy,” said César Muñoz, a senior researcher at Human Rights Watch who looked at dozens of killings with suspected links to land disputes. “The challenge is that because the investigations are really bad, some of the killings that happened should have been counted but weren’t.”

All of the themes that define the broader forest dynamic — lax law enforcement, violence and impunity — have been playing out in the microcosm of Maranhao state. Muñoz visited the state last year to learn about the guardians of the forest, a band of 180 men patrolling the Arariboia indigenous territory. He found that the threat of violence was pervasive. Three guardians had been killed, and many more were being threatened.

“It was very common that indigenous leaders were being threatened by loggers,” he said. “It happened everywhere we looked, and we didn’t find a single case where the authorities had pressed charges for the threats.”

Some of the people facing those threats were Paulino’s family members.

“I’ve had a personal relationship with the family since I was a kid,” said Gil Rodrigues, an official with the Indian Mission Council, affiliated with the Catholic Church. They considered themselves wardens of what they called the “coração da mata,” the heart of the forest.

Paulino was inculcated with those principles from a young age, Rodrigues said. He was a “youngster worried about preserving everything for the future generations.”

He joined the guardians — sliding on a black vest, and wielding a long rifle and long knife — and started patrolling the forest.

“An island in a sea of deforestation” was how Sarah Shenker, a Brazil researcher for the indigenous-advocacy organization Survival International, described their patch. As she visited Maranhao several times in the past three years, she came to know Paulino well.

The last time she saw him was in April, as the dry season was beginning — and as Amnesty International was warning that “blood will be shed” if the government didn’t step in to protect the indigenous.

“I wouldn’t say that he was fearless,” Shenker said. “He, like all humans, had his fears, and one of his biggest fears was being killed. He said he could be killed at any minute — and used to say that all of the time.”

During that April trip, Shenker traveled with the guardians deep into the forest to root out illegal logging. They found a logging camp, recently abandoned. The guardians set it ablaze. Shenker remembered Paulino looking into the flames.

“It made him so angry, that here was this illegal logging camp, and there was trash everywhere, and they were going to profit from this while his people were going to suffer,” she said.

He talked about his fears.

“I’m doing this and I’m putting my life at risk,” he said. “But I see no other way.”

Then he got back to his patrol.