Confederate partisans planned to burn the lower timbers of the 160-foot (49 m) bridge across the river, leaving the top looking intact.
At 11:15 p.m. on a moonless night, the westbound passenger train from Hannibal, Missouri, to St. Joseph started to cross the bridge.
Confederate Major General Sterling Price, who had been invading northern Missouri at the time, wrote Union commanding general Henry Wager Halleck to protest, stating the sabotage was "lawful and proper" according to the rules of warfare and that the captured men should be treated as prisoners of war.
Halleck replied that the bushwhackers were "spies, marauders, robbers, incendiaries, guerrilla bands...in the garb of peaceful citizens".
One of the soldiers killed was Barclay Coppock, a member of John Brown's raid on Harper's Ferry.