A secret John Doe investigation has been opened into the case of a man allegedly beaten by off-duty Milwaukee police officers at an after-hours party in the Bay View neighborhood, sources familiar with the proceedings said. The investigation was convened after several officers declined to fully cooperate with internal police investigators about the early morning incident on Oct. 24, according to the sources, who spoke on the condition they not be named because the proceedings are secret by court order. At the party, a 26-year-old Milwaukee man was severely beaten and, he told investigators, was sodomized with a knife by one of the officers.