People who believe in God often ask athiests; well what happened BEFORE the big bang. And of course athiests will tell them "Nothing". Which is of course the correct answer, because before the Big Bang there was No Time, No Matter, No Nothing ... even. And of course that is a very hard concept to imagine. So perhaps what they should say is ... "Who Created God?".
Of course the real answer to that is "Mankind created God". We invented him/her/them to explain all the things that we could not (at that time) explain.