How should I go about writing this character?

Okay, so I have this character in a novel I am writing that is priving a major stumbling block in how I write him. Mainly, this is because I am so afraid of doing this poorly that as of yet nothing has been written.
The general gist is that he is perceived by the masses as 'insane' due to his erratic behaviour and sociopathic tendencies. In actuality, the cause of this behaviour is his knowledge of the date of the end of the world (an event that will take place well within his lifetime) leading to what I can better describe as existentialism and ultimately nihilism that drives his actions. He seeks to 'soften the blow' of the apocalypse by causing as much suffering as he can. In his mind, making the world to die a terrible one is a kindness.

I have a loose idea of how I should go about managing this: keep scenes of him exclusively through the POV of others until the end where the truth is revealed. It just sounds soo cliche though. Surely there must be a better way.

TL;DR version
How do you write a character that everyone believes to be insane while implying that they are not?
Asked Apr 12, 2014
how about writing the story from his point of view?
Answered Apr 13, 2014

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