Brazil’s President Jair Bolsonaro called Swedish climate change campaigner Greta Thunberg a “brat” on Tuesday, Dec. 10, after her comment on two Indigenous people Brazilians’ death in the Amazon.

The fight ignited on Monday after Thunberg tweeted a link to a story about two indigenous men of the Guajajara tribe in eastern Amazon who were shot dead on Saturday in a drive-by shooting in Brazil’s Maranhao State.

“The indigenous peoples are literally being murdered for trying to protect the forest from illegal deforestation. Over and over again. It is shameful that the world remains silent about this,” the 16-year-old wrote.

Thunberg’s tweet triggered President Bolsonaro anger. “Greta said that the Indians died because they were defending the Amazon,” Bolsonaro told a group of journalists. “It’s impressive that the press is giving space to a brat like that,” he added, using the Portuguese word ”pirralha.”

The teen activist did not seem to give in. She changed the biographical description on her Twitter account to “Pirralha.”

Thunberg’s comments about the death of the indigenous people came as the U.N. was hosting its international climate change conference, where Brazil’s environmental policies have been the subject of criticism. Deforestation of its Amazon rose nearly 30% in the 12 months through July.

One of Brazil’s policies is to reduce tribal rights to land and allow commercial exploitation of their protected reservations. Questioned about the Guajajara murders, Bolsonaro told reporters “any death is worrying.” About the illegal deforestation, he said his government will bring in laws to correct the problem.