Probably a good bet, if there was one survivor, she was the one that interrupted the robbery and was able to escape. Just guessing.
The survivor was a store employee.
http://www.suntimes.com/news/metro/775862,survive020408.article
And now, as many of of have suspected, they are linking the killer to one of the victims.
http://www.nydailynews.com/news/us_world/2008/02/04/2008-02-04_one_of_five_women_in_illinois_bloodbath_.html