Both males are people of the Guardians of the Wooded space, a neighborhood of bigger than 100 tribesmen who try to provide protection to their land from prison logging gangs.
"The blood of Paulino (Guajajara) and so many other indigenous has been and will be shed because those who can prevent the barbarism are silent and do nothing". Another indigenous leader, Laercio Souza Silva, was also hit by gunfire, but managed to escape.
Earlier this year Paulo Paulino told Survival: "It makes me so mad to see this [forest destruction]!"
"There is a lot of impunity".
"Their racist words and genocidal, anti-indigenous proposals give a kind of green light".
Greenpeace said the two males were "basically the most most up-to-date victims of a drawl that refuses to conform with what the constitution determines". "It is time to stop this institutionalized genocide. Stop authorising the bloodshed of our people!"
The Guajajaras, one of Brazil's largest indigenous groups with some 20,000 people, set up the Guardians of the Forest in 2012 to patrol a vast reservation.
Brazilian President Jair Bolsonaro has been recorded several times stating that he does not agree with the number and size of indigenous territories.
Amazon deforestation almost doubled in the first eight months of the year, compared with the same period a year before. Raging fires in the gap made world headlines.
In September, Human Rights Watch said the threats and attacks on forest defenders were "only getting worse" under Bolsonaro.
Bolsonaro has vehemently defended his policies.
Brazil's federal police said they had sent a team to investigate the circumstances around Paulino Guajajara's death.
Sonia Guajajara, leader of the organization, said that the government had been dismantling environmental and indigenous agencies, leaving tribes to fend for themselves as invaders enter their lands.
Shenker, who used to be in the gap in April, said they would preserve Moro to his promise.
"The Brazilian government has to accept that it is their responsibility to protect those lands. That they do not, their absence there, is what pushes the guardians to assume this defense, a very hard and unsafe job", Shenker told AFP.
The Guajajara people of the state of Maranhão knew they were in danger.
Non-profit group Survival International, which advocates for isolated communities, says at least three Guardians have previously been killed, along with many of their relatives, the BBC reported.
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