 SOURCES CONFIRMED TO CBS NEWS POLICE WERE ALERTED TO A SUSPICIOUS PERSON SPOTTED OUTSIDE THE SECURITY PERIMETER. OFFICERS BRIEFLY LOST TRACK OF HIM BEFORE HE REAPPEARED ON THE ROOF OF A NEARBY BUILDING. THE LOCAL SHERIFF CONFIRMED AN ARMED MUNICIPAL OFFICER WAS HOISTED ONTO THE ROOF OF THAT BUILDING BUT FELL OFF WHEN THE SHOOTER POINTED HIS RIFLE IN THE OFFICER'S DIRECTION.