The NIS investigation focuses on "Revolutionary Organization (RO)," the true nature of which was first informed by an internal whistle blower of the UPP. He, identified only as 40-year-old Mr. Yi, is known to have been one of the core members of the insurgent group. Reports said Mr. Yi had been disappointed by North Korean submarine attack on a South Korean corvette "Cheonanham" in March 2010, and the RO's unconditional loyalty to North Korean regime, and he finally decided to reveal the treason plot and get a 'new life.' He allegedly handed in a USB drive containing the RO's doctrine and goal, members' activities, and materials for ideological study. The NIS was reported to have said that Mr. Yi's statements coincide largely with what was found from the subsequent probe.