Situations like this make me wonder why some folks get snakes. You would think that they would fully understand the problems that arise with keeping them. I personally would kill it, freeze it and use it on a later day.
In the future I would suggest purchasing some frozen mice. That way you do not have to deal with the killing, and all this can be avoided. But understand if you cannot kill prey, then do not buy live again. Honestly, something you have to deal with....