THE HELICOPTER (HEL) WAS BEING LOADED WITH THE ENGINES RUNNING. THE FLT CREW WERE AT THE CTLS WHEN THE ACDNT OCCURRED. INITIALLY, 4 PAXS WERE ESCORTED TO THE HEL BY A CUSTOMER SVC AGENT. AS THE 4 BOARDED, THE AGENT RETRIEVED THEIR CARRY ON BAGGAGE. AFT THEY HAD BOARDED (ON THE LFT SIDE), THE AGENT LEFT THE DOOR OPEN, ANTICIPATING A 5TH PAX. HE THEN CARRIED THE BAGGAGE AROUND TO THE RGT SIDE & LOADED IT IN THE BAGGAGE COMPARTMENT. AFT LOADING THE BAGGAGE, HE CAME BACK ARND TO THE LFT SIDE & HELPED LOAD THE 5TH PAX THAT A 2ND AGENT HAD ESCORTED, THEN TOOK A PSN BY THE LEFT MAIN GEAR. REPORTEDLY, THE 1ST 4 PAXS WERE STILL ON BOARD WHEN THE 5TH PAX BOARDED. AFT HE WAS SEATED & SECURED, THE 2ND AGENT LEANED FWD TO THE COPLT'S DOOR TO INFORM HIM OF THE ADNL WT. AFTER A BRIEF CONVERSATION WITH THE COPLT, SHE TURNEDBACK TO CLOSE THE PAX DOOR. AT APRX THAT TIME, ANOTHER HEL PLT SAW A PAX (1 OF THE 1ST 4) WALKING TWD THE TAIL & STARTEDTO TRANSMIT A WARNING TO THE PLT. BFR THE CALL WAS COMPLETED, THE PAX WALKED INTO THE TAIL ROTOR.