Kapos were individuals selected from the camp inmates and given some limited authority, with power over other prisoners. They were responsible for the prisoners placed under them, and therefore could be punished for their escape or misdemeanours.
Frequently these prisoners were selected from among the more criminally-minded of the camp inmates, especially those more inclined to violence. They were often considered more dangerous and volatile than the Nazi camp administrators, partly because they didn't have the same qualms about being "contaminated" by the prisoners. The Kapos were responsible for administering many of the more sadistic and brutal punishments and beatings, and they were avoided by other prisoners. Viewed as traitors by their own people, these individuals walked a fine line between victims and perpetrators.