The South Korean military initially mistook the man who crossed the border into North Korea over the weekend for a defector coming to the South, according to Seoul’s Joint Chiefs of Staff (JCS), delaying efforts to stop him.

Announcing the results of an investigation into the New Year’s Day border crossing, the JCS revealed that the military overlooked critical signs that might have led to an earlier response and different outcome, pledging to take corrective measures to prevent future security lapses.