According to Angela, the real cause was suicide but there's definitely some wiggle room there.
Poor African Issac.
Not a bad episode tonight. I liked the return to Season 1. Though again, I'd rather Sylar made the decision to be evil instead of him being manipulated or having "the hunger" It makes his redemption must more compelling.
The last scene with Arthur was awesome but I find him to be a very one-dimensional bad guy.