Untitled Sighting

I began my morning like most, waking up & heading to the bathroom.  Sorry to get so descriptive in the following sentence but I'd like to include all details.  As I was sitting on the toilet seat, I happened to look outside the window and saw what I thought was an ape steadily running along the backyard fence.  As soon as it came into my view, I thought to myself, "What in the world. . .?"  So, I opened up the window and poked my head out to follow where it was headed.  It was about 5ft. 5 in. and it ran at a steady pace.  The way it ran also made me conclude that it could not have been a human as well as it wasn't an ape.  For one, when people run, we tend to usually lose balance, stumble over hilly like ground, etc.  Since the area in my backyard is covered with leaves, huge branches, etc. you're bound to trip over something (especially since it's very forest like.)  And that was what astonished me.  The creature ran as if it were running on flatland with both arms positioned like most runners do.  It was jet black all over, hair very straight but not long.  Then I listened out for it while having my head outside the window.  It ran very silently but I noticed after it was out of my site about a minute later, I heard sounds of rocks knocking together coming from further into the woods.  Although it resembled closely to an ape, I've now realized it could not have been that either.  Apes usually run on all fours even though they're able to stand on 2 legs.  This creature ran on 2 legs the entire length of the backyard, like a human would run. (Never tripping or falling.)