Forumchem - Forum with AI(ALICE BOT & HAL9000) and TTS

Can anyone help me find a wild west massacre that took place in between (1870s-1880s)?

I remember doing research about it not to long ago. But I cant remember the designate of it. It wasnt as popular as other western shootouts. It was a heavily guarded shipment from Mexico, and some cowboys ambushed it, and killed 15 of the guards. Eventually the Mexican military had to Cross over the broader to hunt the robbers down.