when did she get that knife? there's not much time between his last alive picture and the accidental ceiling shot. i think she had the knife with her while she was taking those pictures---very close by. maybe she went in the kitchen and got it when he went to get into the shower?
(i go with shot last only because there was so little bleeding from the wound and i don't know that he could've resisted, stumbled and crawled like he did if he'd already been shot in the head.)
at any rate, we just know she DID shoot him and we'll never know for sure when. even if the defense tries to say this wasn't that awful because she shot him first, we KNOW he was trying to get away from her and she was stabbing him in the back as he went. that sounds pretty awful to me.