Gettysburg's First Casualty On June 26, 1863, while scouting the area around Gettysburg, Confederate cavalry came upon a small group of Union Troopers of the 21st Pennsylvania Cavalry south of town. Private George Washington Sandoe fired at the Confederates, and they fired back. The Union trooper fell dead. Shown here with his wife, Diana, he was the first Union soldier killed at Gettysburg. Sandoe had been in the army for six days.