IF the husband harmed Shanann and the kids, I'm thinking it was not premeditated, due to the fact that Nicole witnessed Shanann going into the house, and a neighbor's camera recording the activity outside the house. ...Unless he is very stupid and didn't think about neighbors' cameras.
I'm thinking, again IF he harmed the family, that during the "emotional discussion" he snapped, enraged (much like Crystal McDowell's ex did when she arrived to pick up the kids). After this he felt he needed to take care of the kids...it's possible they were awake from the noise, maybe even witnessed an altercation (God forbid), or smothered them with a pillow. Then got the three of them into the truck and drove off, and got back by 5:15 am.
Or...there was an accident with one of the kids earlier in the night, an accident that looked really bad and suspicious, and once Shannon came home....he had to deal with her and the other child.
I don't know.....just can't get over the fact that no one but him were seen living the locked up house. Increasingly hard to give him the benefit of the doubt.