Audio pataje

This happened a few years ago, and I still can’t explain it. I was home alone one night, just watching videos in my room. My parents were out, and my brother was staying at a friend’s house. So the house was completely empty. Or at least… that’s what I thought. Around 1 AM, I heard something downstairs. At first, I ignored it. I thought maybe it was just the fridge or something falling. But then I heard it again. A slow… heavy… footstep. Like someone was walking. I froze. I took off