In Peter Cozzens’ book This Terrible Sound: The Battle of Chickamauga on page 492 there is the following description of the death of Colonel Edward King:

…Thirty minutes earlier, a sharpshooter’s bullet had cut him down. “I well remember our men begging Colonel King to dismount and not expose himself needlessly, as several shots had been fired at him while sitting on his horse,” a member of the Nineteenth Indiana Battery lamented. King finally relented. He slid down off his horse—right into the path of an oncoming bullet. Struck above the right eye, King died instantly.

In the endnotes Cozzens gave two sources for this story. The first one is High, Edwin W.,History of the Sixty-eighth regiment, Indiana volunteer infantry, 1862-1865, with a sketch of E. A. King's brigade, Reynolds' division, Thomas' corps, in the battle of Chickamauga; Published by request of the sixty-eighth Indiana infantry association, 1902. Published: [Metamora? Ind.] . Pages 94-96.

The second one is Chickamauga National Park. Indiana at Chickamauga, 1863-1900, report of Indiana commissioners Chickamauga national military park. Indianapolis, Sentinel print. co., 1900. Pages 199-200.