Sickles became increasingly nervous, knowing that his troops were facing an unknown number of Confederates to the west. A patrol of Jackson's troops was driven back by Union gunners, a minor incident that would come to be exaggerated into a heroic repulse of Jackson's entire command. Between 11 p.m. and midnight, Sickles organized an assault north from Hazel Grove toward the Plank Road, but called it off when his men began suffering artillery and rifle friendly fire from the Union XII Corps.^[12]

Stonewall Jackson wanted to press his advantage before Hooker and his army could regain their bearings and plan a counterattack, which might still succeed because of the sheer disparity in numbers. He rode out onto the Plank Road that night to determine the feasibility of a night attack by the light of the full moon, traveling beyond the farthest advance of his men. When one of his staff officers warned him about the dangerous position, Jackson replied, "The danger is all over. The enemy is routed. Go back and tell A.P. Hill to press right on."

As he and his staff started to return, they were incorrectly identified as Union cavalry by men of the 18th North Carolina Infantry, who hit Jackson with friendly fire. Jackson's three bullet wounds were not in themselves life-threatening, but his left arm was broken and had to be amputated. While recovering, he contracted pneumonia and died on May 10. His death was a devastating loss for the Confederacy.