Ask Mr. Smarty Plants

If it is a native shrub, you can search for it in our Native Plant Database by doing a COMBINATION SEARCH.  Choose "Tennessee" from the Select State or Province option and "Shrub" from Habit (general appearance).  This will give you a list of 150 species with thumbnail photos to do a preliminary search.  When you find a photo that is similar to the shrub, you can go to the species page to see a description and more photos.  I assume that the shrub is evergreen since you mention leaves and berries together.  You can also limit your search to evergreens under the heading Leaf retention.  I didn't find any evergreen shrubs that matched your description, but you should look through them yourself.     Here also is a webpage from Eastern Tennessee Wildflowers showing shrubs with fruits to look through.

The fact that you saw the shrubs at a shopping mall, however, is likely to mean that they are a cultivated import.  One shrub that comes to mind is Nandina domestica (heavenly bamboo).  Although it is an attractive evergreen shrub it, unfortunately, is listed by Invasive.org.  Here is more information about the invasiveness of heavenly bamboo from Texas Invasives.  If it is heavenly bamboo, we would hope you wouldn't want to try to grow it in Illinois because of its potential invasiveness.  Additionally, its "hardiness" is listed by Floridata as being Zones 6 to 9.  Clarksville, Tennessee appears to be in the USDA Hardiness Zone 7a; but Peru, Illinois in La Salle County appears to be USDA Hardiness Zone 5b.  Heavenly bamboo would probably have a difficult time growing there anyway since your temperatures fall below those of Zone 6.