There is a name-by-name casualty report for the 22nd Alabama Regiment in the Battle of Shiloh, available in National Archives microfilm M836. Since there is no record of John Hood being a casualty at Shiloh in his military service file, I must assume he wasn't injured in that battle. The service file shows that he died of disease.

The service file for Stephen R. Hood includes an order by General Bragg directing that Capt. Hood be discharged from service on the basis of a surgeon's certificate of physical disability. The captain's actual letter of resignation with the surgeon's comments are not on file. Could be that Capt. Hood's age (forty-three or forty-four) and physical constitution were the basis for the discharge. Being a minister, he like many of his men may have been unused to life in the open.

Since Bragg's order authorizing Hood's resignation was issued on Jan. 1, 1862, the resignation may have been submitted at least a week or more earlier.