on April 7 in a car accident in Guatemala. She was 68.
Killed in the car with her were Ana Paula Hernández, 42, a fellow human rights worker from Mexico, as well as Ana Velásquez, 22, a Guatemalan human rights advocate, and the driver, Daniel Tuc, 43, also Guatemalan.
Ms. O’Neill and Ms. Hernández were in Guatemala on behalf of the Fund for Global Human Rights, a nonprofit organization based in Washington that supports local activists in 16 countries, including many in Latin America.
At the time of the accident, which occurred in the Huehuetenango region of western Guatemala, they were visiting some of the fund’s grantees, Regan E. Ralph, the fund’s president and chief executive, said in a telephone interview. Ms. Ralph said that the road was dangerous and visibility low when the car went off a cliff.
Ms. O’Neill had worked for the fund as a part-time consultant for four years. She had spent most of her career, 37 years, working for Trocaire, the overseas development agency of the Roman Catholic Church in Ireland, with a concentration in Latin America. She officially retired in 2015 and started consulting for the fund. She also continued to work voluntarily with prisoners and migrants in Honduras, where she lived with her family.
In 1982 she and Michael D. Higgins, then a member of the Irish Parliament and now president of Ireland, were among the first outsiders to visit the village of El Mozote and investigate reports of a massacre there.
They found evidence of the systematic torture, rape and slaughter of civilians, who were subsequently confirmed to have been killed by death squads and by Salvadoran Army soldiers trained and supplied by the United States.
The New York Times and The Washington Post published prominent articles about the killings. “It is clear that a massacre of major proportions occurred here last month,” The Times reported in January 1982.
The Reagan administration, which was backing the Salvadoran government with military and economic aid in an effort to counter a leftist insurgency, dismissed reports of the massacre, calling them Communist propaganda.
It was not until 1993, long after Ronald Reagan had left office, that a United Nations truth commission report, relying on classified documents from the United States government, concluded that groups of men, women and children had been tortured and “deliberately and systematically executed.”
Mr. Higgins said in a statement after Ms. O’Neill’s death that “when I visited Central America as president of Ireland in October 2013, she was present to hear the massacre — long denied — recognized as genocide. She was pleased to see the names of the dead remembered, and to meet the relatives of those killed.”
He added that as a human rights advocate, Ms. O’Neill was “relentless in calling on those with power to bring their influence to bear on the policies and politics that affected those most vulnerable.”
Ms. O’Neill was born in Dungannon, County Tyrone, in Northern Ireland and moved to Belfast when she was 18 to attend college. She then took a job in Latin America, where, she told The Irish News in 2018, she was working on a project, and traveling up the Amazon River when her party had to pull over to a small indigenous village because of rough rapids.
“A charity was working there on a health program, and I remember being instantly impressed with the work they were doing,” she said. The charity was Trocaire, and she joined it in 1978, just five years after its founding. She became an integral part of the organization’s growth and development.
She was soon leading delegations of Irish politicians and bishops to Central America so they could see the atrocities resulting from brutal civil wars in El Salvador, Guatemala and Nicaragua. She also served as a translator for Archbishop Oscar Romero of San Salvador (who has since been declared a saint by the Catholic Church), six weeks before his assassination in 1980.
“Sally was the heartbeat of Trocaire for almost 40 years,” the agency’s chief executive, Caoimhe de Barra, said in a statement.
In addition to her work in Central America, where she oversaw humanitarian aid to more than two million refugees, Ms. O’Neill worked in Ethiopia and Somalia during famines there and took charge of the agency’s humanitarian efforts in Vietnam, Cambodia and Laos.
She had seven siblings, all of whom survive her. She is also survived by her husband, Roger, and their children, Roger, Rhona and Xiomara.
Ms. O’Neill’s first grandchild, Patrick, was born the day before she died; the day she died was her 40th wedding anniversary.
Ms. O’Neill and Ms. Hernández were traveling in Guatemala to report on its current political crisis. In January the country’s president, Jimmy Morales, withdrew from a United Nations-backed anticorruption commission and gave its international prosecutors a day to leave Guatemala. Among other things, he and his allies are seeking to release scores of convicted human rights abusers, including perpetrators of massacres, from prison, undoing a generation’s worth of efforts to bring them to justice.
The two women were also there to support local human rights activists and others in the face of repression and attacks, David B. Mattingly, the fund’s vice president for programs, said in an email.
Ms. Hernández joined the fund full time in 2011 as the program officer for Latin America, providing strategic support and funding to scores of human rights organizations in Mexico, Guatemala, Honduras and El Salvador.
Ms. Hernández earned her bachelor’s degree in sociology from the Ibero-American University in Mexico City and her master’s in human rights and democracy from the Latin American Faculty of Social Sciences in Mexico. In 2010 she was named a Yale World Fellow. She lived in Mexico City.
She worked for 15 years in the field of human rights in Mexico, including six years at the Miguel Agustín Pro Juarez Human Rights Center in Mexico City and four as deputy director of the Tlachinollan Human Rights Center in the state of Guerrero. Among her activities was working with families of the disappeared in Mexico and visiting with indigenous communities in Central America that were resisting the mining companies encroaching on their land.
Little information was available on the others in the car. Ms. Velásquez was working as a representative of the Mayan Peoples’ Congress of Guatemala. She was not connected with the fund but was getting a ride with the others. Mr. Tuc, a longtime driver with the fund, had three children.