You might consider reading up on the Fort Pillow Massacre. Confederate Cavalry under Nathan Bedford Forrest stormed a fort in Tennessee in April 1864 and killed the members of the garrison even as the attempted to surrender because the garrison was made up mostly of United States Colored Troops, along with numerous African civillians.

Or the Lawrence raid when Bushwhackers under William Quantrill burned 1/4 of Lawrence Kansas killing about 150 men and boys in 1863.

Slavery?

Just noticed the typo in my title. I meant "and/or" instead of "are". My bad.