Mathew saw to many people he loved die. He couldn't watch more people get slaughtered by Herobrine. Even the mobs in Minecraft hate him. That's why Herobrine needs to be stopped... But this time forever.
Their plan: death. That's all they want. They want us dead so they sent it. Now we survive. Not their plan. But who knows and who cares when you are in a zombie apocalypse.