The 9th Illinois history refers to “Captain Sleepers' Guerrillas” at the time. He enlisted in Gordon’s 2nd Ark. Cav. later as a 2nd Lieutenant June 14, 1862.

Full text of "History of the Ninth Regiment Illinois Cavalry Volunteers. Pub. under the auspices of the Historical Committee of the Regiment .."
https://archive.org/stream/historyofninthre00illi/historyofninthre00illi_djvu.txt