Minecraft: Why is Herobrine being nice to me?

I just happened to be in the forest collecting Wood for my house and when I walked in, Herobrine was standing by my fireplace I'd built earlier that day and when I backed away (cause I think he's evil) he just started giving me Diamonds and never stopped for Half an Hour in the real world and then he gave me a Diamond Sword and continued giving me Diamonds for the whole day. I even went to mine some Stone, get some Meat and and a few Apples and Flowers and he followed me around and didn't attack or kill me and killed some Creepers and Spiders I encountered at night cause I needed some more Wood for my house. He never leaves me alone and often helps cut down trees with me, and grab things I need. He even went out to the village I was by and grabbed some things I wanted. I have absolutely no Mods installed and this was a clean save I had. Why is he being so nice to me. I even look at him and see he's always got a happy face on (which is rare to see). I have the 'Steve' skin on.