We may not know exactly why or how University of Virginia student Otto Warmbier fell into a coma while imprisoned in North Korea. He died six days after the North Koreans shipped his nearly lifeless body home. US and South Korean officials estimate that 80,000 to 120,000 prisoners are being held in these camps. The North Korean government says they don't exist. Although Warmbier's fate is tragic, it is not unusual - for North Koreans.