Some indigenous groups in the Amazon rainforest say they are increasingly vulnerable to incursions by loggers and cattle ranchers.
Both men are members of the Guardians of the Forest, a group of more than 100 tribesmen who attempt to protect their land from criminal logging gangs.
The Brazilian Justice Minister said the government would spare no effort to find those responsible.
Paulo Paulino was shot within the neck and died within the jungle, in keeping with the Worldwide Survival group, who stated his accomplice was injured however managed to flee.
Survival Global researcher Sarah Shenker said: 'Violence and death threats against the guardians were going down for years.
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's time to stop this institutionalized genocide!"
It is the latest incident in a wave of violence targeting indigenous land protectors since the election of Brazil's far-right President Jair Bolsonaro a year ago. "Stop authorising the bloodshed of our people!"
She said they informed federal agencies "but they didn't take any action".
A logger additionally died within the assault Friday night time in Maranhao, a northeastern state, in accordance with FUNAI, a state company that represents indigenous pursuits. We don't break into their houses and rob them, do we? "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 Bolsonaro government has indigenous blood on its hands", Brazil's pan-indigenous organization APIB, which represents numerous country's 900,000 native people, said in a statement on Saturday.
The Arariboia territory is home to about 5,000 indigenous of us - the Guajajara and the Awa. Officials say federal police will investigate Guajajara's death.
"Maranhao state understood how the urgency of the situation in view of the federal government's failure to act, nearly in connivance with the attackers by encouraging the invasion of reservations", said national indigenous leader Sonia Guajajara.