I ENTERED THE PARKING LOT OF A GAS STATION AND PUT THE VEHICLE IN PARK BUT LEFT THE ENGINE RUNNING. I EXITED THE VEHICLE AND WHEN I RETURNED 30 SECONDS LATER I FOUND IT HAD ROLLED 50 FEET AND STRUCK A BUILDING. INSTEAD OF "PARK" I FOUND THE VEHICLE IN "NEUTRAL". NOBODY WAS INJURED BUT I HAVE DAMAGE TO MY VEHICLE AND PROPERTY DAMAGE TO A LIBRARY.