First off, welcome to the site!! Start reading up on this site and asking questions and trust me you will learn ALOT!! I learn something new every day by visiting this site.
If you are talking about watching a snake kill a mouse being disturbing, actually it is recommended to feed f/k (fresh killed) or f/t (frozen thawed) mice or rats anyway. One thing you will have to be careful about is since you have a rat any time you handle the rat you should wash your hands and change your clothes if the rat was on you at all. The snake could smell the rat on you and think it's feeding time!!