Yoo's body too badly decomposed to determine cause of death; mystery surrounding final days of de-factor owner of doomed ferry deepens. Yoo's son arrested in latest capture of family members. South Korea's forensic agency said on Friday it was impossible to determine the cause of death of a businessman linked to a ferry that sank and killed 304 people in April, deepening the mystery surrounding the final days of Korea's most wanted man. An autopsy and DNA tests on the badly decomposed body of Yoo Byung-un revealed no evidence that he was poisoned, and there was also no indication of external trauma, forensic agency chief Seo Joong-seok told a news conference.