There where many things that lead up to the massacre of the 23 union soldiers, and the battle that followed. Something that preceded the massacre was the attack on union soldiers at the Skirmish of Goslin Lane. This is where Anderson stole union uniforms. Those stolen uniforms where possibly used for stopping trains. Which is how they stopped the train and massacred those 23 union soldiers. One of the final things that led up to this attack was Anderson's past and his hatred for the union.
These are photos of union uniforms that where similar to the ones stolen
People have been looking into this skirmish, for some time. They think that this is the mass grave where the union soldiers where buried.