José Godoy, the former Mayor of the city of Mérida, Chiapas, and a leader of the Workers' Coalition, had announced that the Coalition's convention would be open, "and not the secret affair of the Anglos," referring to the earlier conventions held by the Continentalist and Liberty Parties, which had nominated the Anglo candidates George Vining and Thomas Rogers.
Godoy was also reputed to be a lieutenant of Carlos Concepción, the leader of the Moralistas guerrilla movement, and rumors began to spread that Concepción himself would appear at the convention. As the opening day approached, the city of Palenque was infiltrated by Mexicano newcomers, along with Anglos and Hispanos who were later identified as members of the Constabulary, a newly-established secret police force created to combat the Moralistas.
On the morning of the convention, as Godoy began to give a speech, Constabulary agents entered the hall, marched to the podium, and arrested him. This led to a riot on the convention floor by Coalitionist delegates, which turned into a panic when gunshots began to be fired. By the time the hall had been cleared, twenty-three Coalitionists were dead, including Godoy. An additional seventy-give people were badly injured, including ten Constabulary agents.
Godoy's death and the Massacre of the Innocents at Montezuma Hall led to uprisings in the Chiapan countryside that eventually spread throughout the United States of Mexico. President Vining reponded by declaring martial law throughout the country, thereby setting the stage for the Night of the Caballeros of 16 September 1881, when Constabulary Commandant Benito Hermión seized control of the Mexican government. Hermión went on to rule as dictator of Mexico for the next twenty years.
Sobel's sources for the Massacre of the Innocents are Orrin Macon's The Palenque Convention in Mexican History (Mexico City, 1960); the 18 and 19 July 1881 issues of the Palenque Pueblo; and the 19 July 1881 issue of the Mexico City Times.