Last month the UN's expert on indigenous peoples' rights called for a stop to the ranchers' violence and 'campaign to spread psychological terror', demanding urgent action to protect the Guarani. But the Brazilian authorities failed them.
A Guarani Indian leader has been shot dead in west-central Brazil, one week after his community reoccupied part of their ancestral land.
Semião Vilhalva was killed on Saturday during an attack on Nanderu Marangatu community, by gunmen hired by ranchers - and reportedly in the presence of government agents.
A one-year-old baby was also struck in the head by a baton round, and others are reported injured.
The community's ancestral land in the state of Mato Grosso do Sul is now occupied by a ranch owned by Roseli Silva, leader of a ranchers' union which encourages violence to keep the Indians off their land.
The Guarani allege that Saturday's attack was coordinated by Silva, following a meeting in which ranchers and politicians discussed how to tackle the Guarani reoccupation.
The Guarani association Aty Guasu released a statement saying: "These ranchers and politicians are encouraging hatred, violence and the killing of Guarani people. They are cruel and must be punished!"
The moments following the murder were recorded on video by Marcelo Zelic and posted on Facebook.
Brazil's government ignores plea for help
Amid escalating tensions last month, the United Nations expert on indigenous peoples' rights, Ms. Victoria Tauli-Corpuz, called for a stop to the ranchers' violence and "campaign to spread psychological terror", demanding urgent action to protect the Guarani,
The appeal came as gunmen were surrounding several Guarani communities, and threatening them with imminent attack. A Guarani spokesman from one community, Tey'i Jusu, warned that the gunmen are patrolling daily, and that "conflict could break out any moment now ... We'll die for our lands if we have to."
But the Brazilian authorities failed to provide the necessary protection. Now the ranchers are attempting to prevent the Guarani from burying Semião on their ancestral land. The Indians are demanding protection from the state to bury him and to prevent further deaths.
The indigenous peoples' human rights group, Survival International (SI) has been is lobbying the Brazilian government to uphold its legal obligations to protect the Guarani and map out their ancestral land for their exclusive use, before more lives are lost.
"What's particularly harrowing about this murder is that the Guarani knew their reoccupation was likely to end in death", said SI Director Stephen Corry. "But despite the ranchers' promise of bloodshed, despite the many killings that have gone before, Semião's community were undeterred.
"Why? Because the land they're reoccupying belongs to them. Brazil recognized this years ago, but is too beholden to lobbyists to uphold its pledge to return the land. Until it makes good on its promise, more innocent lives will be lost."
Decades of land theft goes unpunished, uncorrected
Several Guarani leaders have already been assassinated as a result of their quest to return to their land - stolen from them decades ago and now occupied by ranches and soya, corn and sugar cane plantations.
Brazil's constitution requires the government to map out all indigenous territory and return it for their exclusive use by 1993, but the majority of the Guarani's land remains in the hands of the ranchers.
Most Guarani are forced to live in overcrowded reserves or roadside camps where malnutrition, disease and suicide are rocketing. Thousands of Guarani holding on to tiny patches of their ancestral land are living in fear of being forcibly evicted.
New video footage (embedded below) also reveals ranchers threatening military police and government agents and accusing them of attempting to "smuggle" a Guarani man back onto his own land.
More film clips are available from Tribal Voice, Survival's groundbreaking new project which brings the latest communications technology to remote tribal communities to enable them to send video messages about their lives and their struggle to survive to a global audience in real time.
The Guarani are one of the first tribes to participate in Tribal Voice, and have described the project as their "newest weapon" in their land campaign.
Act now to help the Guarani
Your support is vital for the Guarani's survival. There are lots of ways you can help.