Paulino Guajajara, a member of an indigenous group in northern Brazil, was shot dead in an ambush by illegal loggers on Friday according to leaders of the Guajajara tribe.
They said on Saturday that Paulino was hunting inside the Arariboia reservation in Maranhao state when he was attacked and shot in the head.
Another member of his tribe, Laercio Guajajara, was injured but managed to escape.
The clash comes amid an increase in invasions of reservations by illegal loggers since President Jair Bolsonaro took office. Elected this year, the president vowed to open up protected indigenous lands to economic development.
Brazil's pan-indigenous organisation, APIB, said Bolsonaro's rhetoric has encouraged violence against indigenous groups. "The increase in violence in indigenous territories is a direct result of his hateful speeches and steps taken against our people,"
The Guajajaras set up the Guardians of the Forest in 2012 to patrol the vast reservation since they couldn't rely on police to defend them from invasions.
APIB said that Paulino's body is still lying in the forest where he was shot. Police have sent a team to investigate the circumstances of his death.
Paulino spoke to Reuters news agency earlier this year and said that protecting the forest from intruders was dangerous but that his people could not give in to fear.
"I'm scared at times, but we have to lift up our heads and act. We are here fighting," he said.
"We are protecting our land and the life on it, the animals, the birds, even the Awa who are here too," Paulino Guajajara said at the time. "There is so much destruction of Nature happening, good trees with wood as hard as steel being cut down and taken away."
"We have to preserve this life for our children's future," he said.