[@Majoras End] what time period are you intending this Alice be from? Only for the simple fact that I feel like a purge is slightly unrealistic. If you're wanting to go along the lines of her having a mental break from her family being murdered you could actually just have a person break into her home and have murdered her family. Her having seen it would cause a break resulting in her attacking said person. 

If you wanted her to have a feeling of guilt maybe it could be a person who have been stalking her. It wouldn't be something that was her fault but as a result of her family dying she would blame herself. Once again this is just an idea.
Other ideas could include terrorist attacks. Or war I suppose.

That being said I don't understand if you are thinking Purge like the movie, or just a civil war one side purges the other kind of thing.