Even atheist scientists agree on the idea that if God does exist then we can't ask who created him because the concept of everything having coming from something is bound to our laws of physics.
The same Hawking you're referring to published a book last year(The Grand Design) on how quantum fluctuations may explain how our universe emerged from a pre-existing universe with the big bang.
Here's a quote form the book:
“Because there is a law such as gravity, the Universe can and will create itself from nothing. Spontaneous creation is the reason there is something rather than nothing, why the Universe exists, why we exist.”
He might be right and he might be wrong. However, I think that it could be quite a valid explanation.
