Why is herobrine in my world?

I was making an underground house then i needed more wood for the walls when i was at the stairs i saw herobrine just staring at me then he disappeared. I tried to forget it i thought someone put a mod on my minecraft so i continued to get wood when i came back my house was missing. My house was right in the middle of a forest and a desert so i know where it is then i died for no reason and spawned right next to my house i never saw herobrine again oh i forgot he took all my things out of my chests my diamonds and gold and he made a floating house above mine out of diamond and gold i was so scared and mad. So i'm hoping you can find an answer why. I don't know how to add a photo but i will when i find out.