Benoit's last acts certainly sound like he did go nuts. Here is my take on the Bibles. Yes, it is speculation:
Benoit was close to Eddie Guerrero right? Both his wife and his kid were killed upstairs. I think Benoit wanted Nancy and Daniel to end up wherever Eddie was, regardless of his position on religion. Maybe killing himself downstairs was some kind of implication that he belongs in Hell (or at least below Nancy, Daniel and Eddie).
It's really sad how these moments of "sickness" can overwhelm even the strongest of us. I want to say that Benoit should have had someone to help him through this, but I'm sure Dean, Chavo and others would have been there. This was just a case of evil showing its face on Earth.
To what BDC said.