This is kind of old news, but something I hadn't heard. Just awful. She was probably killed more for being an environmental activist than a nun, but this is completely callous. This is from May 15, 2007. From the BBC:
A Brazilian rancher has been found guilty of killing US-born nun and environmental activist Dorothy Stang.
A court in the city of Belem sentenced Vitalmiro Bastos Moura, 36, to 30 years for paying gunmen to shoot the 73-year-old missionary dead in 2005. Sister Dorothy campaigned for poor farmers' rights and to preserve the rainforest from loggers and developers. Her murder followed a dispute with ranchers over land they wanted to clear for pasture and she wanted to protect.
Judge Raymond Moises Alves Flexa imposed the maximum sentence. He said Moura had showed "a violent personality unsuited to living in society" and that the killing had been carried out in a "cowardly manner". Activists saw the trial as a test of whether the government could act to curb lawlessness in the Amazon.
Dorothy Stang's brother David, who was at the trial, said "justice was done".
Prosecutors said Mr. Moura had ordered Sister Dorothy's killing because she had sent letters to the local authorities accusing him of setting illegal fires to clear land, which led to him receiving a substantial fine.
The Ohio-born nun had lived in the remote town of Anapu for more than 20 years, helping peasant farmers defend their land. She was found dead on a muddy track in February 2005, shot six times at close range. Three men - two gunmen and an intermediary - have already been convicted for the killing, but this was the first trial of someone who ordered it. Another rancher charged with ordering the killing goes on trial later in the year.
In the past 30 years, more than 1,000 people have been killed in land disputes in Brazil, the BBC's Brazil correspondent Gary Duffy says - more than 770 of those in the state of Para.