Paulo Paulino Guajajara, known as “Wolf”, was attacked while hunting in the Arariboia reservation in Maranhao state
He was shot in the face and another member of the Guajujara tribe was wounded but escaped.
Mr Guajajara was one of the leaders of the Guardians of the Forest, which was set up by the Guajajara tribe in 2012 to protect the Amazon rainforest from intruders.
His death comes amid growing concern over the policies of right-wing President Jair Bolsonaro, who has vowed to open up protected indigenous lands to economic development.
“The Bolsonaro government has indigenous blood on its hands,” said Brazil’s Indigenous People Articulation (APIB), a group which represents many of the country’s 900,000 native people.
“The increase in violence in indigenous territories is a direct result of his hateful speeches and steps taken against our people.”
APIB leader Sonia Guajajara said the government was dismantling environmental and indigenous agencies, and leaving tribes to defend themselves from invasion of their lands.
“It’s time to say enough of this institutionalised genocide,” she said in a post on Twitter.
Brazil’s federal police said they had sent a team to investigate the death and Sergio Moro, the justice and public security minister, said they would “bring those responsible for this crime to justice”.
However APIB said his body was still lying in the forest where he was killed.
Mr Guajajara had previously told reporters about the danger he faced trying to protect the rainforest.
“I’m scared at times, but we have to lift up our heads and act,” he said. “We have to preserve this life for our children’s future. We are protecting our land and the life on it, the animals, the birds... there is so much destruction of nature happening, good trees with wood as hard as steel being cut down and taken away.”
Additional reporting by Reuters
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