According to Fray Juan Pobre in 1602, Sinaro was a Chamorro from the village of Guaco, Rota. Sinaro speared a Spaniard named Sancho after being ridiculed and humiliated by him. Apparently Mågå'låhi Sunama of Tazga was Sancho's master or friend.
Sancho died from his wound and Sunama's family gave him a Chamorri burial. Spears were placed in the ground in front of Sancho's grave as a symbol of alerting the people of Tazga and warning the people of Guaco that they would avenge Sancho's death. Even Mågå'låhi Toca of Guaco denounced Sinaro as a bad person.
As a cultural practice of what seemed to have been a form of Chamorro justice, Sinaro made a trip to Guam to retrieve a tortoise shell, a few fish, and other things to offer Sunama and his family in an attempt to make amends over Sancho's death.
Judith R. Amesbury & Rosalind L. Hunter-Anderson. 2003. Review of Archaeological and Historical Data Concerning Reef Fishing in the U.S. Flag Islands of Micronesia: Guam and the Northern Mariana Islands (Final Report). Western Pacific Fishery Management Council.
Lawrence Cunningham. 1992. Ancient Chamorro Society. Best Press: Hawaii