I PLACED MY 2014 GRAND CHEROKEE OVERLAND (4 MONTHS OLD 1900 MILES) IN PARK AND LEFT IT RUNNING WHILE EXITING TO GET MY MAIL FROM MY MAILBOX. UPON EXITING, I VALIDATED MY JEEP WAS IN PARK ON THE SHIFTER. IT DID NOT MOVE WHEN I LET OFF THE BREAK (ON COMPLETE LEVEL GROUND), THE BACKUP CAMERA DISPLAY WAS NOT PRESENT, AND THE VEHICLE DID NOT CHIME WHEN EXITING TO SHOW THE VEHICLE WAS STILL IN GEAR. I DID NOT HAVE THE EMERGENCY BREAK ACTIVATED. I WALKED 50 FEET TO MY MAILBOX AS I NOTICED THE VEHICLE WAS ACCELERATING IN REVERSE TOWARDS MY NEIGHBOR'S HOUSE. I RAN AFTER IT AS IT DROVE THROUGH MY NEIGHBOR'S LANDSCAPING AND WAS READY TO RUN INTO HIS GARAGE DOOR. I CAUGHT UP TO THE VEHICLE, JUMPED IN IT SIDEWAYS TO HIT THE BREAK, WAS THROWN OUT OF THE VEHICLE AND IT SLAMMED INTO THE GARAGE DOOR. HAD I NOT PARTIALLY STOPPED THE VEHICLE PRIOR TO FULL IMPACT, THE DAMAGE WOULD HAVE BEEN EVEN EXTENSIVE. LUCKILY I JUST HAD MINOR CUTS AND BRUISES AND NO ONE ELSE WAS HURT, BUT THERE WAS DAMAGE TO THE REAR PASSENGER SIDE BUMPER OF MY JEEP (STRESS MARKS AND PAINT DAMAGE) AND I HAD TO REPLACE MY NEIGHBOR'S FULL GARAGE DOOR. I TOOK MY JEEP INTO MY DEALERSHIP THE NEXT DAY (10/13/14) AND THEY SAID THEY COULD NOT REPEAT THE ISSUE, HOWEVER, THEY HAD TO APPLY A TRANSMISSION SOFTWARE UPDATE THAT CONTROLLED DOWNSHIFTING GEAR RATIOS ABOUT COMING TO A COMPLETE STOP. I FIND THIS IRONIC THIS HAD NOTHING TO DO WITH MY TIMELY TRANSMISSION ISSUE. AS I HAVE SEEN MANY MORE CASES AND NEWS STORIES REPORTED ON THIS IS