Its going to be impossible for him to get off with the murder charge and have it reduced, here is a man who had obviously over time courted the idea of some kind of abduction of April or some other kid by the way he encroached on their lives on various fronts, social networking,observing as well as depraved images leading to some form of fantasy scenario he wanted played out.
It could well be the case that at some point April became free and he ran her over then as he isn't clear about the order events happened. The disposal of the body was pretty calculated also.