Minecraft: Anomaly

I'm writing this here because some strange stuff happened to me in my minecraft world. I'm documenting things that happened in this little story.

So, after creating a brand new world, I did the usual. Get wood, make a house, mine things, get stone, etc. In the middle of getting stone tools, I come across this huge cave system. I mined some stone, created an entire set of stone tools, and went into the cave system. Everything was normal at first. I found iron, smelted it, created some iron tools, fought zombies, skeletons, etc. After a little bit of experience grinding in this cave, I end up seeing this strange shadow. It looked like a player, but that couldn't be possible...

I was playing in single-player mode, so there was no way that anyone could join my world. I decided to follow it. It lead me to an abandoned mineshaft. After placing down torches, collecting loot, and killing mobs, I find this one weird block. It was entirely white at first, but then it flashed between different models and textures. I saved at that moment, before interacting with it.

After saving it, I decided to break it. I picked it up, and the item name was all screwed up. I placed it back down, and I decided to actually touch the block this time. A strange, reddish steve appeared in front of me, looking down at me. I first didn't care, because, this thing wasn't attack me, it was just staring at me. Then, it had a bucket of lava in it's hand, and placed it down all over the mineshaft. The mineshaft caught on fire, and I ran as fast as I could, but went to a dead end. The thing is back to staring at me, and i'm confused.

"This thing literally tried to kill me, then stops trying to? What the hell is going on!?" Eventually, it disappeared all-together. No trace of it. The mineshaft wasn't even on fire. Was it just a hallucination? I'm confused about the event to this day, wondering what just happened. I hope I get an answer someday.