Alfonso VI, from his exile in Toledo, obtained the support of the Leonese nobility and his sister Urraca, who remained strong in the city of Zamora, a lordship that Ferdinand I had granted her previously. When Urraca refused to exchange Zamora for other cities that Sancho had offered her in an effort to control the fortress of Zamora, "key to the future expansion south of the Duero", Sancho besieged the city. However, during the siege, Sancho II was murdered. According to tradition, during the siege a nobleman named Vellido Dolfos appeared before the king, claiming to have changed his loyalty from Urraca to Sancho. Under the pretense of showing him the weak parts of the city's walls, Dolfos separated the king from his guard and killed him with a spear. Although there is no clear evidence that Sancho II's death was due to treason rather than deceit, since Dolfos was Sancho II's enemy, his murder occurred in a warlike attack during the siege, not near the city walls, but rather in a nearby forest where Dolfos lured the Castilian king away from his armed protection. The violent death of Sancho II, who had no descendants, allowed Alfonso VI to reclaim his throne as well as Sancho's and Garcia's original inheritances of Castile and Galicia, respectively.