Good question! We don't know anything about what happened in the VD home that morning, do we? Damon got up at sometime (when?) fixed a little something for one or both of the boys (who walked past her open bedroom door?). Brenda got up (when?) did what? made coffee? read the paper? did some laundry? tripped over the dog bed? asked Damon what happened to it? asked why? recapped the previous evening?
We know nothing about any of this, not even their carefully constructed lied. Maybe Feldman will recall them and work backwards from the 911 call with the barking dog and screaming alarm recorded.