There are several newspaper accounts of this gunfight, for example, the National Police Gazette 3-8-1879. Accounts differ slightly, but it goes about like this:
About 10 days prior to the gunfight, Holman had entered Dr. (not general, that was his brother) W. L. Lowry's store in Johnsonville. Lowry ordered Holman out, remarking that H was no gentleman and didn't keep his word. H departed in a rage.
H boarded the steamer Sunflower that morning accompanied by his father in law Dr. G. C. Walker, and when it stopped in Johnsonville, L boarded to transact some business. H saw L, grabbed him and shot him. L's clerk, John Arnold, and L, shot back, killing Dr. Walker. L died about 2 minutes later. Arnold was killed in the fusilade, and H wounded.
The Atlanta Constitution 2-18-79 and the Vicksburg Herald also had stories on the shooting.