Well, it's about as easy to fracture the temporal bone as it is to fracture a rib (and many a person has taken many a punch to their ribs without fracture - usually needs to be a sharp, focused blow or a pretty good fall). The side of the head (which is what I believe they mentioned in this case) would be more like breaking a thigh bone. Even karate experts cannot, with their hands, easily break a thigh bone and it takes a big, muscular person a really good kick to do it.
If Suspect was sitting down in a car, I doubt he could have thrown a punch like that (although if she couldn't get out of the car and he threw many punches...maybe). Much more likely he would use a blunt instrument (which is why they said blunt force trauma). Many household objects or items could be used. Merely fracturing a skull will not create brain bleeding sufficient to cause death. The fact that the coroner says that the blow was strong enough to cause death (and skull fragments were found in two places) tells me that it is very unlikely it was merely a blow from his hand. That posits boxer skills and super human strength (which he obviously would have loved to claim having, but I do not think that's what happened).
They will probably find evidence on some object taken from his house, given how ridiculously stupid he was in hiding evidence.
