Why did the southern states form slave patrols?

Slave patrols called patrollers, patterrollers, pattyrollers or paddy rollers,[1] by the slaves, were organized groups of armed white men who monitored and enforced discipline upon black slaves in the antebellum U.S. southern states. The slave patrols' function was to police slaves, especially runaways and defiant slaves. They also formed river patrols to prevent escape by boat. Slave patrols were first established in South Carolina in 1704, and the idea spread throughout the colonies.