Sgt Hayes and the doc seem to know each other and have worked together before. She would know that Hayes is married with a pregnant wife.
It makes no sense that Sarah would rely on a key above the door jamb to get into her own house, especially being short and pregnant. She would have a house key with her car keys like anyone else.
Sgt Hayes has to be the worst cop possible. Doesn't bother trying to take fingerprints or DNA from these people to identify them. Doesn't check the cemetery for more people. Doesn't properly clear the bathroom before being attacked. Lets his wife keep walking to edge of town without stopping her. When he does tell Vic what happened, and Vic thinks him crazy, he doesn't offer any proof, just walks off.