Knowing very well that this was just a 150 word story for a challenge, I still want you to write more of it. If we could participate in the contest, this would be the winner. I bow to your talent

This story has a lot of potential to be very chilling, but I think naming the body in the first line really hurts it. It might help you a lot to move it around, maybe towards the end. I feel like once I read "Mrs Jones" I can figure out the rest of the story: oh, she killed someone she knew. Also, the use of "a-calling" seems really out of place and could be shortened to just "calling." I know that none of this advice can help you in the competition now, but just to give you some pointers that might be applicable to your future works.