Why is Herobrine in Minecraft?

There was a myth that Notch put Herobrine into minecraft as a memorial for his brother who died right before the Minecraft game was released. They say he took it out, but people still say they see him today.

But of course Notch doesn't have a dead brother and the creator of "Herobrine" admitted it was a hoax.
You can still get the Herobrine using the "Humans+" Mod and spawn him with the "Single Player Commands" Mod. It's ID is 3008 and is friendly towards you until you smack him. He attacks all other creatures and sadly does not build his own wooden houses.