Why was kansas called "bleeding kansas?"?

Bleeding Kansas is the term used to described the period of violence during the settling of the Kansas territory. In 1854 the Kansas-Nebraksa Act overturned the Missouri Compromise’s use of latitude as the boundary between slave and free territory and instead, using the principle of popular sovereignty, decreed that the residents would determine whether the area became a free state or a slave state. Proslavery and free-state settlers flooded into Kansas to try to influence the decision. Violence soon erupted as both factions fought for control.