Captain Constantin Blandowski, commanding Company F, Third Missouri Volunteer Infantry Regiment, was shot in the leg at Camp Jackson on May 10, 1861. Most accounts claim he was struck by a shot from a pistol wielded by a member of the crowd. With one of his soldiers already dead and uncertain of the threat of mob action, the wounded Blandowski gave the order that began the deadly firing on the crowd of civilians at Camp Jackson.

After receiving the gunshot wound at Camp Jackson on May 10, 1861, Blandowski was taken to the U.S. Arsenal for treatment. He was moved to the Good Samaritan Hospital, where on May 23 he endured the amputation of the wounded leg. The surgery proved to be too great a shock. He weakened and died three days later on Sunday, May 26, 1861.

Thus, Constantin Blandowski became the first officer of the Union army to be mortally wounded in the Civil War.

Blandowski was born on October 8, 1828, in Prussia, near the border with Poland. Blandowski was a revolutionary who took part in the uprisings in Europe in the late 1840s. Blandowski fled to America. Arriving in the United States in 1850, he made his way west through New York, Philadelphia, and Cincinnati to St. Louis, probably making his living by giving lessons in fencing and in other arms. 

For those of you wondering, the more famous Colonel Elmer E. Ellsworth was killed on May 24, 1861 while removing a Confederate flag from the roof of a Virginia hotel.