"Cause apocalypses."

He says it like everyone's gone and done it in their lifetime.

"I've been through quite a few of them, was the catalyst for most of them. So, this time around what you see is what you get—I haven't quite figured it out, but I'd say around mortal drinking age."

There are other reasons he hasn't quite figured it out, but no one really admits to killing their former incarnation. It's a bad line.