As investigators tallied bullet casings, sought surveillance tapes and talked to witnesses, one thing remained unclear to a community left reeling from a Saturday's deadly shooting spree: Why?The gunman's motive for shooting dead a bicyclist and two women living in a home for recovering addicts remained a mystery Monday, even as police released the names of each victim killed along the half-mile rampage.Andrew Alan Myers, 35, was shot while riding his bicycle on Prospect Street, his body falling mere feet from the house where the gunman lived.