28th Regiment, Louisiana Infantry (Gray's)
28th Infantry Regiment was organized during the spring of 1862 at Camp Bisland, Louisiana. The men were recruited in the parishes of Bienville, Winn, Ouachita, Jackson, Claiborne, and Calcasieu. For a time it served in the Department of Mississippi and East Louisiana, and in the fight at Chickasaw Bayou it lost 9 killed, 25 wounded, and 9 missing. Later the unit was assigned to Mouton's and H. Gray's Brigade, Trans-Mississippi Department. It was involved in the operations against Banks' Red River Campaign and in numerous conflicts in Louisiana. In July, 1862, it contained 25 officers and 278 men, but few were present during the spring of 1865 when the unit disbanded. The field officers were Colonels Henry Gray and Thomas W. Pool, and Lieutenant Colonel William Walker.
This site has much information on the regiment as well as a good roster: http://www.penandsaber.com/grays28th/
King, William H. "No Pardons to Ask, Nor Apologies to Make; The Journal of William Henry King, Gray's 28th Louisiana Infantry Regiment." [Ed by Gary D. Joiner, Marilyn S. Joiner & Clifton D. Cardin] Knoxville, TN: U TN, 2006. 322 p.
http://www.abebooks.com/servlet/SearchResults?sts=t&tn=No+Pardons+to+Ask&x=85&y=16
Additional information may be obtained through a Goggle Search "Gray's 28th Louisiana Infantry"
You may procure his service record file at http://history-sites.com/research/index.html