Note: Photo included. Contrite St. John's Univ. student behind alleged massacre threats on Facebook says booze to blame BY KERRY BURKE DAILY NEWS STAFF WRITER Thursday, September 17th 2009, 3:34 PM PHOTO CAPTION: "Radames Santiago Jr., 18, a student from St John's, who was arrested for making threats on his Facebook page." SNIPPET: "A St. John's University freshman who posted messages on Facebook threatening to launch a "Virginia Tech attack" at the Queens campus told the Daily News that he was just drunk and never would have caused anyone harm." SNIPPET: "Santiago, who lives in Washington Heights with his mom...