In an unprecedented clash with their own people, PLO police fired on Palestinian demonstrators in Gaza City -- killing 13 people and setting off riots aimed at undermining PLO chairmanYasser Arafat's increasingly shaky rule. TIME reporter Jamil Hamad, who was on the scene, says about 200 people were wounded, at least 30 seriously, when the police strafed demonstrators protesting the arrests of 160 Islamic extremists. Outside a nearby hospital, angry Palestinians screamed, "Arafat, traitor," and "Arafat, killer" as two police cars and a movie theater were set on fire. "All the accusations are pointed at Arafat, not the major or colonel who gave the orders," says Hamad, noting that the PLO leader's ties to Israel makes it irrelevant to his foes whether he directly ordered shootings. Police apparently fired on the crowd of 6,000 demonstrators -- mostHamassupporters -- when one officer was hit by a stone.TIME Jerusalem Bureau Chief Lisa Beyersays Israelis had been asking Arafat to go after armed militants, but "they did not ask him to open fire on crowds. That's not exactly a surgical way to combat Islamic fundamentalism in Gaza."