On July 30, 1866, black freedmen are parading with a marching band outside a convention in New Orleans, post-Civil War, where white Republicans are securing voting rights for black people. However, an armed mob of white men — including active police and many Confederate veterans — opposed to suffrage for anyone but themselves has also gathered. The mob begins shooting at the freedmen, many of whom attempt to take cover in the convention hall. The mob surrounds and enters the hall, shooting and beating black people and convention delegates until the floors are slick with blood. Even corpses are mutilated.

Federal troops arrive to quell the violence but between 34 and 200 people — almost all black — have been killed. The event increases support nationwide for the Fourteenth Amendment.