THE HELICOPTER WAS REGISTERED TO THE U.S. ARMY AND BEING OPERATED BY THE U.S. CUSTOMS SERVICE. A WITNESS LOCATED ABOUT 5 MI SOUTH OF THE ACCIDENT SITE STATED HE HEARD A HELICOPTER FLY OVERHEAD TOWARDS THE NORTHEAST, UP THE ALTAMAHA RIVER, AT ABOUT 1030. THE HELICOPTER WAS TRAVELING FASTER THAN MOST HELICOPTERS, AND WAS FLYING VERY LOW AT TREETOP LEVEL. A POWER OUTAGE OCCURRED AT 1033. THE HELICOPTER HAD COLLIDED WITH UNMARKED WIRES 82 FT ABOVE THE RIVER. THE PIC DID NOT COMPLETE A RISK ASSESSMENT WORKSHEET FOR THE ASSIGNED MISSION NOR WAS IT APPROVED BY THE APPROVING AUTHORITY. THE COPILOT'S INJURIES WERE CONSISTENT WITH BEING ON THE FLIGHT CONTROLS AT THE TIME OF IMPACT.