Mexican bandits led by Pablo Lopez, aligned with revolutionary Pancho Villa and operating in de facto government territory of Villa's rivals, the Constitutionalists—stopped a train in Santa Isabel and removed from it around 17 American citizens who were employees of the American Smelting and Rifling Company.
During the early years of the Mexican Revolution, from 1912 to 1914, the revolutionary Pancho Villa had aligned with Venustiano Carranza to form the Constitutionalists, an army that successfully rebelled against the "inefficient dictatorship" of Victoriano Huerta.
Villa badly lost these battles, and fled with his army to the northern Mexican mountains, while Carranza controlled Chihuahua with his de facto government.
Villa ordered the execution of the Americans in the Santa Isabel massacre "to demonstrate that Carranza did not control northern Mexico".
The Constitutonalists found on Lopez's person a diary entry in which he states he was ordered by Villa to commit the massacre, as well as a book belonging to Tom Evans, one of the murdered victims.
[2] Because of the massacre and the raid on Columbus, U.S. president Woodrow Wilson ordered a military expedition into northern Mexico led by General John J. Pershing.