A gun-toting nut wandered East Flatbush, pistol-whipping a passerby, vandalizing an elementary school and even pointing the gun at his own head, new video released by the NYPD shows. The disturbing series of events began just after 8 p.m. Friday near Lefferts and New York avenues in Brooklyn when the unidentified man pistol-whipped a 23-year-old...