Well, 'god is a bullet novel' could potentially revolve around a story where the presence of a higher power, symbolized by 'god', has an impact similar to that of a bullet. A bullet is fast and can change things in an instant. Maybe in the novel, the actions or influence of this 'god' - like entity are sudden and far - reaching, altering the lives of the characters in a very decisive manner. It could also be a story set in a world where the concept of god is as dangerous or as liberating as a bullet.
I don't think it is. 'God Is a Bullet' seems to be more of a fictional concept than based on an actual true story. It could draw some loose inspiration from various sources, but not a single, verified true account.
I don't have a clear answer on that. It could potentially draw elements from various sources, but without specific information, it's hard to say for sure.