The digging of the grave was always unclear. The affidavit states that MM witnesses the holes being dug "on or about April 27". That could be the afternoon after the murders. It isn't really clear.Didn't he dig the grave before the murders? I thought I read that. He may not have planned the murder of the daughter, but I think he planned to murder the mother. I think he hoped everyone would think she ran off with the girls.
He may have planned the murders, it's still questionable to me, though. Or he may have planned the murders, just not there.