THE BALTIMORE POLICE DEPTARTMENT PILOT WAS SUPPORTING UNITS ON THE GROUND, AND AFTER COMPLETING AN ASSIGNMENT, HE STARTED A CLIMB. DURING A CLIMB THROUGH APPROXIMATELY 200 FEET AGL, A LOSS OF ENGINE POWER OCCURRED OVER A HIGH DENSITY RESIDENTIAL AREA. WHILE MANEUVERING TO AVOID OBSTACLES DURING AN AUTOROTATION, HE LOST ROTOR RPM AND MADE A HARD LANDING IN A STREET INTERSECTION. THE ENGINE WAS TEST RUN SATISFACTORILY AND THE CAUSE OF THE POWER LOSS WAS NOT DETERMINED.