The mail man/post man comes on Sundays around Xmas time .. I reckon it was the wife !! She killed for insurance reasons and greed is always the killer MONEY !
did op even give out the answer? op said they'd give it out at 9 am. its way past 9 am. even for est.
The maid cause there are no post on sundays. Hahahaha. I'm so late in answering. Anyway i just wanted to guess. ?