 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.