Terrifying Encounter at Joshua Tree National Monument-1979

Photo courtesy of National Geographic.

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A witness reports that they and a companion had an unusual and terrifying encounter with something unknown and unseen, yet heard, in the Joshua Tree National Park in 1979. 
No footprints were found but there were 3 round depressions left in the gravel.

Please note that the report is "as is", with no corrections.

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MUFON Case # 30355
Date:    1979-03-31
Location: Joshua Tree, California
Shape:    Unknown
Vallee Index:    CE1
   
Report:
Arrived at Joshua Tree National Monument friday evening to camp and do some rockclimbing for the weekend. It was very windy and cold and the sun had set. We set up camp with a small 2-man tent (without windows)and were sitting inside discussing what to do about dinner since it was too windy to light the camp stove.
We had only been in the tent about 10 minutes when a soft whirring (hard to describe) sound flew directly over the tent and stopped what sounded like 20 to 25 feet away. As we looked at each other, asking simultaneously "did you hear that", we could hear foot steps approaching from the direction the strange noise had stopped. They were clearly discernable as bipedal walking on the decomposing granite as it came toward the tent. The foot steps circled the tent twice and stopped at the zipper door and proceeded to sniff the entire zipper(the door was an inverted T). Then nothing. I probably don't need to say we were thoroughly frightened out our wits.
Not exactly sure how long we sat listening but seemed like forever that we sat waiting for that door to open or at least hear more footsteps but we heard nothing. Finally whispering to each other we decided to make a run for the car which was only 10 feet away.
We unzipped the door and ran on the count of three, jumped in the car and locked the doors. We turned on the lights and looked around and saw nothing. After we calmed down, we got out the flashlights and started looking around for anything including footprints, there were only ours from setting up the tent. We headed out the direction that the sound came from and the only thing we found was a set of three round depressions in the gravel approximately 10-12 feet apart in a triangular pattern, also with no footprints around them.
Don't really know what to think...

Photo courtesy us-parks.com

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