DURING A SKYDIVING OPERATION, THE AIRCRAFT WAS SLOWED TO SLOW CRUISE FLIGHT FOR A PARACHUTE JUMP. AS SKYDIVERS WERE MOVING TO THE EXIT DOOR FOR A GROUP JUMP, THE D-RING OF ONE SKYDIVER'S RESERVE PARACHUTE BECAME ENTANGLED ON A PROTRUDING CABIN DOOR SUPPORT BRACKET. THE RESERVE CHUTE DEPLOYED & WAS CAUGHT IN THE SLIP STREAM. THE SKYDIVER WAS THEN PULLED FROM THE OPEN DOOR. HE IMPACTED THE RIGHT HORIZONTAL STABILIZER, FELL 4000 FT TO THE GROUND & WAS FATALLY INJURED. MOST OF THE RIGHT STABILIZER WAS TORN FROM THE AIRCRAFT. AFTER ITS SEPARATION, THE AIRCRAFT ENTERED A DIVE & THE REMAINING SKYDIVERS JUMPED FROM THE PLANE. ONE OF THE OTHER SKYDIVERS WAS IN THE DOORWAY WHEN THE ACCIDENT SEQUENCE BEGAN. HE HELD ONTO THE AIRCRAFT FOR A MOMENT AS IT SHUDDERED & STARTED TO DIVE, THEN 'LET GO.' DURING THE OCCURRENCE, HE RECEIVED A MINOR INJURY. THE PILOT REGAINED CONTROL OF THE AIRCRAFT & MADE AN EMERGENCY LANDING AT AN AIRPORT WITH A LONG RUNWAY.