Bonner is best known as one of two journalists (the other was Alma Guillermoprieto of The Washington Post) who broke the story of the El Mozote massacre, in which some 900 villagers at El Mozote, El Salvador, were slaughtered by the Salvadoran army in December 1981.
On December 11, 1981, the Atlacatl Battalion occupied the village of El Mozote and massacred at least 733 and possibly up to 1,000 unarmed civilians in what became known as the El Mozote Massacre.
In January, 1982, Guillermoprieto, then based in Mexico City, was one of two journalists (the other was Raymond Bonner of The New York Times) who broke the story of the El Mozote massacre in which some 900 villagers at El Mozote, El Salvador, were slaughtered by the Salvadoran army in December, 1981.