Anyone can
say they believe in God, but if their actions and behaviour are not consistent with their profession of belief, then, in fact, they don't believe at all. If they did, their conduct would be commensurate with it.
My uncle was in the Western Desert during WW2. He said that there were no atheists in foxholes. He said the "atheists" bragged about how they didn't believe in any god, but when the air raid came over, they leap into their foxholes and prayed like crazy!!
This shows me that just because a person says they are atheists, if their behaviour under stress is not consistent, then they don't really believe that there is no God somewhere out there.