North Korean leader Kim Jong Un’s half-brother Kim Jong Nam had been working with the CIA as an informant prior to his death, according to a report by the Wall Street Journal on Monday.The Wall Street Journal reported that Nam had a “nexus” with the US spy agency, citing an anonymous “person knowledgeable about the matter” as a source. Nam met with CIA operatives on multiple occasions, but not much is known aside from that. US officials have told the Wall Street Journal that Nam did not know much about the inner workings of North Korea.A book set to be published on Tuesday by Anna Fifield, Washington Post’s bureau chief in Beijing, refers to Nam’s ties to the CIA. “King Jong-nam became an informant for the CIA … His brother would have considered talking to American spies a treacherous act. But King Jong-nam provided information to them, usually meeting his handlers in Singapore or Malaysia,” she wrote.Nam was the eldest son in the current generation of North Korea’s ruling family, and would have been the heir to supreme leadership had he not racked up a reputation as North Korea’s only international playboy. He had spent the majority of his youth in Moscow and Geneva where he learned to speak different languages and drove expensive cars. In 2001, he was caught by Japanese officials after using a false name—”Fat Bear” in Chinese—in his passport. He was eventually exiled in Macau and indulged in a lifestyle of gambling and frequent travel.Nam was murdered on Feb. 13, 2017 at the Kuala Lumpur International Airport in Malaysia two hours after liquid VX, a banned nerve agent, was smeared on his face. Two women were charged for the crime. Indonesian Siti Asiyah, was released on March after getting her charges reduced, whereas Vietnamese Doan Thi Houng was released last month. US and South Korean officials have said that North Korean authorities ordered his assassination. Pyongyang has firmly denied such allegations.