The composed image in this date’s post would almost lead one to believe it posed, but Mexican campesinos Arcadio Jiménez, Hilario Silva, and Marcelino Martínez really were all shot together at Chalco on this date in 1909, for killing a policeman during the tense twilight of dictator Porfirio Diaz, on the verge of the Mexican Revolution. It’s believed to have been taken by Augustin Casasola.
From this lengthy dissertation pdf. (See the 384th page of the pdf, or page 354 as numbered within the document.)
According to Photographing the Mexican Revolution: Commitments, Testimonies, Icons, the event was luridly covered by the magazine El Imparcial, which described the execution in these words:
The bodies fell simultaneously, slowly backward, and a hoarse whisper flowed from either the enormous holes made by the bullets or their tightly pressed lips. The clothing smoked from the gunpowder, and their contractions denoted an extraordinarily cruel suffering. A death rattle, like that of a sheep with its throat cut, escaped from the three bodies. Their families sobbed, and their cries filled the countryside. Those of us who were present will never forget it.