For your Black Hawk War ancestor you should visit the Illinois State Archives website (bravo to Illinois!) at http://cyberdriveillinois.com/departments/archives/databases.htmlhttp://cyberdriveillinois.com/departments/archives/databases.html and click on the Database of Illinois Black Hawk War Veterans link. You may submit a lookup request and they'll try to find your ancestor in the book The Black Hawk War 1831-1832 by Ellen M. Whitney.
Aaron Gunn was an early settler of LaSalle County. He purchased land from my ancestor...as quoted in the book "Biographical Sketches of Bureau County, Illinois" (pub. 1885): "William Hall settled where Lamoille now stands in 1830. He sold his claim to Aaron Gunn and removed to Indian Creek, where he was killed by the Indians." (That's my ancestor, William Hall, who was killed by Indians, one of the victims of the Indian Creek Massacre.)
I've seen Aaron Gunn's name in a few other LaSalle County histories, including this article from 1868...http://www.piperspages.com/Putnam/OldPutSettler.htm.