MOUNT KISCO, N.Y., Sept. 6 — A village police officer was charged on Thursday with second-degree manslaughter in the death of a homeless Guatemalan immigrant four months ago that had shaken this community of 10,000 people. The officer, George Bubaris, also faces one count of unlawful imprisonment and two counts of official misconduct, according to an indictment unsealed in Westchester County. In a news conference on Thursday, the Westchester district attorney, Janet DiFiore, refused to detail what investigators believe transpired between Officer Bubaris and Mr. Perez, other than to say that Officer Bubaris, “while on duty as a Mount Kisco...