Believing that his forces were firing on friendly soldiers, Confederate Brig. Gen. Felix Zollicoffer rode forward with an aide to ascertain the situation and was subsequently killed by Union troops

The identities of several of the troops on the Mill Springs Battlefield were obscured by smoke and rain. Brig. Gen. Felix Zollicoffer instructed his 19th Tennessee to cease its fire after becoming convinced that his soldiers were firing on other Confederate forces. He then rode forward with an aide to assess the situation.

Colonel Speed Fry of the 4th Kentucky, a Union regiment, also rode forward during one of those bizarre battlefield encounters, and he and Zollicoffer (or his assistant) engaged in conversation without realizing they were speaking to an enemy officer. They were asked to halt the friendly fire by the Confederates. Fry concurred. One of the two Confederate officers soon realized his error and fired his revolver at Fry. This pistol fire, hitting Fry's horse but missing Fry, convinced the adjacent 4th Kentucky men that these two mounted officers were Confederates. Both Zollicoffer and his assistant were instantaneously murdered by the Union soldiers' hail of gunfire. Zollicoffer's careless ride into the midst of his enemies had cost him his life and his death greatly demoralized the Confederate soldiers.