Police searched Sunday for four people suspected in the slaying of a 74-year-old American nun — the most prominent activist gunned down in the Amazon since the 1988 murder of Chico Mendes.

Dorothy Stang (search), who spent decades fighting efforts by loggers and large landowners to expropriate lands and clear large areas of the Amazon rainforest, was shot dead early Saturday near Anapu, a rural town about 1,300 miles north of Sao Paulo.

She was killed less than a week after meeting with Human Rights Secretary Nilmario Miranda (search) to report that four local farmers had received death threats from loggers and landowners.

Land ownership in the Amazon rainforest is often disputed by loggers, landowners and local peasants. The government grants land titles, but deeds are rarely respected.

Police refused to identify the suspects Sunday, but said they believed two hired gunmen had carried out the crime at the behest of two others.

An autopsy performed Sunday in Belem determined that Stang had been shot six times — in the head, throat and abdomen. Her body was expected to be sent back to Anapu on Monday for burial.

Claudio Guimaraes, director of the state's forensics institute, said shots appeared to have been fired from half a meter — just over 1½ feet — away.

Outside the morgue, dozens of protesters from church and human rights groups sang hymns and held up plaques demanding justice in one of the country's most lawless regions, where illegal logging, slave labor and violent land conflicts are common.

Stang, who had been raised in Dayton, Ohio, defied the frequent threats to her own life.

"She was on a list of people marked for death. And little by little they're ticking those names off the list," said Nilde Sousa, of the Para state Movement for Women, who worked with Stang.

Brazil's Environment Minister Marina Silva compared Stang's death to the 1988 murder of Chico Mendes (search), the renowned rubber tapper who called international attention to the destruction in the Amazon rainforest.

"When he died a lot of people celebrated. The two were searching for the same ideal," said Silva, who worked with Mendes in their native state of Acre.

Stang had worked in the Anapu region for more than 20 years. She was a naturalized Brazilian citizen and an outspoken critic of efforts by loggers and landowners to take control of land — often through phony deeds — to clear large tracts of rainforest for the lumber and to produce grazing land for cattle.

The Rev. Robson Lopes (search), who worked with Stang in the region since the early 1990s, said she was murdered in the Boa Esperanca settlement, which the government reportedly had granted to local peasants but was coveted by loggers. Police said two gunmen shot Stang as she accompanied two rural workers to a meeting to discuss a settlement.

The two workers fled and were not hurt.

Greenpeace estimates that about 90 percent of the lumber produced in huge Para state is cut illegally. Experts say that as much as 20 percent of the 1.6-million-square-mile Amazon rainforest has been destroyed.