1. The first soldier killed in the war died entirely by accident.
The opening salvos of the Civil War were fired during the siege of Fort Sumter in South Carolina. When P.G.T Beauregard accepted the surrender of the fort, there were zero fatalities on either side. When the Union troops lowered the American flag, they gave it a 100-gun salute.
An accidental discharge from a cannon firing that salute killed Pvt. Daniel Hough of the 1st US Artillery.