YANGON The man regarded as the fourth most powerful member of Myanmar's military government was killed on Monday when a helicopter carrying several high-ranking officials crashed into a river in bad weather, Reuters quoted state media as saying. Myanmar television and radio said Lieutenant General Tin Oo, secretary two of the ruling State Peace and Development Council (SPDC) and chief of staff of the army, was killed in the crash at the Salwin River in Kayin State, east of the capital Yangon.