Herobrine wasn't always mean and didn't steal peoples stuff. He used to be a hero. So he had a brother named Steve. Steve was doing a challenge if he died then his minecraft world would be deleted. Steve was mining diamonds when he accidentally fell onto a ledge. He screamed for help but no one could hear him but Herobrine. The lava started to rise and Steve thought he would lose his world forever. That wasn't the case. Herobrine came to the rescue grabbing Steve by the hand saving him. They mined diamonds together having fun. When they returned to their two Herobrine was famous. Everyone liked him but he got so much attention he became greedy and mean. He started stealing peoples stuff and instead of the smiles on the other player's faces they were frowns. Herobrine got used to being mean and greedy that he began going to peoples worlds and haunting them. One day while Herobrine was annoying people someone with a powerful sword better than diamond hit Herobrine in the face and his eyes turned white. Herobrine then was blind temporarily and started hitting people and terrorizing them with TNT.

Okay this isn't what really happened and I don't think anyone knows why Herobrine shows up in people's worlds(I actually know I think) but it's a nice story isn't it?