SAO PAULO (Reuters) - Indigenist Maxciel Pereira dos Santos was murdered execution-style before members of his family in the Amazon town of Tabatinga, according to INA, a union group representing workers at Brazil’s indigenous protection agency FUNAI, on Sunday.

Santos was shot twice in the head on Friday as he rode a motorbike down a main street of Tabatinga, located deep in the Amazon rainforest on Brazil’s border with Colombia and Peru, the Folha de S.Paulo newspaper reported.

In a statement, INA cited evidence that his murder occurred in retaliation for Santos’ role in combating illegal invasions by hunters, loggers and gold miners in the Vale do Javari reservation, home to the world’s highest concentration of uncontacted indigenous tribes.

Folha de S.Paulo said police were investigating whether Santos’ death was related to his work at FUNAI but did not have enough information to determine the motivation behind the crime.

Santos served more than 12 years at FUNAI, including five as chief of environment services at the Vale do Javari reservation, INA said.

Funai has three bases in the Vale do Javari to protect an area the size of Austria with some 6,000 residents from eight tribes, and some 16 uncontacted tribes.

INA called on authorities to demonstrate Brazil “no longer condones violence against those who engage, under the rule of law, in the protection and promotion of indigenous rights.”

It also urged authorities to protect agents who protect indigenous lands.