Miner1.jpeg

i was searching through my old computers files the other day to get all nostalgic and such, i went to the "Minecraft" file to see some stuff from me in the 5th grade and i saw this video file i had never remembered making called "Miner1.jpeg" and it was dated November 8, 2015 about a year after i got the game. I was curious so i clicked the file and it came up with the game's protagonist "Steve" or me at the time walking up a hill in a big hills biome, I chopped some trees got some wood and cobble, etc. then i paused the video at around the 3:47 mark and saw this weird figure stalking me from the cave tunnel i had made, It was a single player world so i was confused. It was just staring at me from around a corner, I guess i couldn't see it at the time so i just turned left and kept mining for about a minute until the video ended, The skin for this player was completely black and i was confused not seeing any skin like it before. Any explanations?