A disputed story over President Bush's National Guard service cost four more CBS News employees their jobs Monday. Viacom's ( VIA) CBS ousted three executives and a producer Monday over their role in the story, which ran Sept. 8 on "60 Minutes Wednesday." Longtime anchorman Dan Rather, who reported the piece, said last November that he would step down in March , though he said the decision wasn't linked to the scandal. The segment claimed that President Bush disobeyed an order to appear for a physical exam, and that friends of the Bush family tried to "sugar coat" his Guard service. After initially brushing off criticism of the piece and its sourcing, CBS in mid-September started an investigation into the matter. The network later acknowledged that the report was based on documents whose veracity couldn't be confirmed . On Monday, CBS said Senior Vice President Betsy West, "60 Minutes Wednesday" Executive Producer Josh Howard and Senior Broadcast Producer Mary Murphy were asked to resign. The producer of the piece, Mary Mapes, was terminated, CBS said. The moves came as an independent panel concluded that CBS News failed to follow basic journalistic principles in the preparation and reporting of the piece. The panel also said CBS News had compounded that failure with a "rigid and blind" defense of the report. CBS drew charges of political bias for running the piece during the presidential campaign. The panel indicated it found no evidence of bias, CBS said. The panel said a "myopic zeal" to be the first news organization to broadcast a groundbreaking story about the president's National Guard service was a key factor in explaining why CBS News had produced a story that was neither fair nor accurate and failed to meet internal standards. "We deeply regret the disservice this flawed '60 Minutes Wednesday' report did to the American public, which has a right to count on CBS News for fairness and accuracy," said CBS President Leslie Moonves. On Monday, Viacom rose 49 cents to $38.15.