Kim Kyung-il, the mayor of the South Korean border city of Paju, was getting ready to tuck in to bed last month when he learned that a high-profile activist was nearby, preparing to launch balloons carrying anti-regime leaflets toward North Korea.

Concerned that the launch might exacerbate border tensions, the mayor concluded that special police tasked with monitoring such activity were too far away to intervene, and decided to take matters into his own hands.