Before his murder, North Korean ruler Kim Jong Un’s elder half brother Kim Jong Nam had become “an informant for the CIA,” a new book published on Tuesday states flatly.

The book is The Great Successor: The Divinely Perfect Destiny of Brilliant Comrade Kim Jong Un, by Washington Post Beijing Bureau Chief Anna Fifield. Asia Times received a review copy and a full review is planned in due course.

Although there had been similar reports earlier, they had tended toward the tentative. On the same February 2017 journey during which he was killed at Kuala Lumpur International Airport, Fifield notes, a hotel elevator security camera pictured him with “an Asian-looking man who was reported to be an American intelligence agent.”

That sighting was indeed widely reported, but Fifield says she has gone farther and confirmed the CIA connection.

“His brother would have considered talking to American spies a treacherous act,” the author writes. “But Kim Jong Nam provided information to them, usually meeting his handlers in Singapore or Malaysia.”

This information, she adds in an endnote, is based on “an interview with someone with knowledge of the intelligence who spoke on condition of anonymity.”

Kim Jong Nam was killed by a pair of Southeast Asian women who rubbed on his face two separate ingredients that, together, became a deadly poison. At their trials, the two testified that North Koreans had duped them into the mission by characterizing it as a harmless prank.

After Kim Jong Nam was killed, his backpack was found to contain US$120,000 in cash. Fifield writes that this “could have been payment for his intelligence-related activities,” although another possible source was a gambling business she describes as having been run by the ruler’s estranged sibling.