While en route to the Temecula Valley, Lugo encountered Chief Juan Antonio, leader of a group of Cahuilla Indians, who joined his forces. The two groups set up camp along the Santa Gertrudis Creek. Lugo was to wait for reinforcements from Los Angeles. Learning that Jose Ramon Carillo and a group of men were at the Mission San Luis Ray de Francia, Lugo requested him to provide assistance. Carrillo and his men joined Lugo and Chief Antonio. Word reached the Temecula village that Californios from Los Angeles were headed to the valley and the Luiseñno went east into the canyon and hid.
Lugo sent a few men to find the Luiseño warriors and the men reported back that the Luiseños were hiding. Lugo knew if his men went into the canyon they would be trapped, so he decided to draw the Luiseño out of hiding and into his own trap. Just west of the canyon was a small meadow with rolling hills on either side. The Cahuilla took position on one hill, and Lugo set his men on the other. Carrillo and his men went into the canyon, where they feigned fatigue. Young Indian warriors thought they saw an opportunity to take the Californios. The chiefs tried to calm them, but the warriors attacked the Californios.
Carrillo and his men fled from the canyon into the meadow, pulling the warriors in pursuit. Once the war party was in the meadow, the Cahuilla and Lugo's men attacked the Luisenos, and Carrillo's men turned and attacked as well. Many warriors were killed; others surrendered. A few warriors escaped and headed toward Aguanga.
Lugo turned over the captives to the Cahuilla, their traditional enemy. Lugo and a few men pursued the escaped Indians. When Lugo returned, Chief Antonio had already killed all the prisoners. The Californios and the Cahuilla regrouped at their campsite. Another group of soldiers, led by Diego Speulveda, joined Lugo at the campsite. Sepulveda's men had been delayed in joining Lugo.
After the massacre, the dead Luiseno warriors were gathered up quickly and buried in a common grave near the Temecula village. The Mormon Battalion arrived shortly afterwards ot the area and the Luisenos asked the battalion to guard them as they buried the dead. Historians disagree on how many Luiseno warriors were killed at the massacre. Some report thirty-three and still others report one hundred and twenty-five. The dead were buried at this location.
The Luiseno Indians are today known as the Pechanga Indians.