The violence at Pauma Valley cannot be understood without grasping decades of betrayal that preceded it. The Luiseno people had lived in this region for thousands of years before Spanish missionaries established Mission San Luis Rey in 1798. By 1833, the mission counted a population of three thousand Luisenos who had been converted, baptized, and put to work. When Mexico secularized the missions that year, Governor Jose Figueroa promised the Luiseno three pueblos, including Las Flores and San Pascual. But Pio Pico, appointed to hold the mission lands in trust, eventually claimed Las Flores as his personal rancho. The same Pio Pico would lead the Californio lancers at San Pasqual. For the Luiseno, the theft of their horses by retreating Californio soldiers was not an isolated insult but the latest in a pattern of dispossession. The nearby Kumeyaay, who had their own grievances against Pico, reportedly aided the Americans at San Pasqual precisely because of this long history of distrust.

Jose Antonio Serrano owned Rancho Pauma, the cattle ranch where the eleven lancers sought refuge after the battle. Serrano himself was not present when the soldiers arrived. He had traveled with his fourteen-year-old son Jesus and brother-in-law Jose Aguilar to Pala, where his wife and other children were staying. According to later accounts, Serrano overheard two Luiseno women discussing a plot to seize the Californios before he left, though he apparently did nothing to warn the soldiers. That evening, Chief Manuelito Cota approached the rancho with a group of warriors from the Pauma band. He knocked on the door and introduced himself by name. The Californios knew the chief and believed they had peaceful relations with him. When they opened the door, the chief and his men captured all eleven without a fight. The prisoners were taken first to El Potrero, an Indian rancheria, for the night. The next morning, the party traveled to Agua Caliente, today known as Warner Springs.

At Agua Caliente, Chief Manuel called together the bands of the region for a tribal council. The fate of the eleven horse thieves would be decided collectively. The proceedings that followed reveal how seriously the Luiseno regarded the crime. These were not random soldiers but representatives of the very system that had stripped the Luiseno of their lands, their mission, and their promised pueblos. The tribal leaders debated and ultimately reached a unanimous verdict: the Californios would undergo ritual torture and execution. The names of the eleven men who died that day were recorded: Manuel Serrano, Ramon Aguilar, Francisco Basualdo, Jose Maria Alvarado, Mariano Dominguez, Santiago Osuna, Jose Lopez, Estaquio Ruiz, Juan de la Cruz, Santos Alipas, and one unnamed man identified only as a New Mexican. Their deaths were meant to be a message, a restoration of some small measure of justice for years of dispossession.

Word of the Pauma Massacre reached Mexican forces in Los Angeles within days. General Jose Maria Flores immediately ordered retaliation. He designated Jose del Carmen Lugo of San Bernardino to lead a punitive expedition against the Luiseno. Lugo recruited Cahuilla warriors as allies, a rival tribe with their own complicated relationship to the Luiseno. The force tracked down the warriors responsible for the killings. What followed was carnage far exceeding the original massacre. An estimated thirty-three to forty Luiseno warriors died in what became known as the Temecula Massacre, including the chiefs who had authorized the earlier executions. The cycle of violence had come full circle, leaving both sides bloodied. Within months, the Mexican-American War would end with American victory. The Luiseno would face decades more of dispossession under their new rulers. Today, Pauma Valley remains home to the Pauma Band of Luiseno Indians, who still tell the story of what happened here in December 1846.