This is the letter purportedly written by Jon Byong Ho, a longtime confidant of the father and son who have ruled North Korea since 1948. Jon is an inside player who rarely travels, and his signed documents have been seen by few officials outside North Korea, making it impossible to authenticate the letter with complete certainty.

But U.S. officials confirm that he long directed North Korea’s defense procurement and nuclear weapons efforts, putting him in a position to know about the events the letter depicts.

The letter opens with the author’s condemnation of the death of the wife of North Korea’s then-top representative in Islamabad, Gen. Kang Tae Yun. She was struck by shotgun pellets while standing beside her husband, and the letter blames U.S., South Korean and Pakistani intelligence agents — an accusation that all three governments have rejected.

A U.S. intelligence official said the letter’s correct account that a North Korean with experience in four countries would replace Kang is among the details that convinced him of its authenticity. Others, including a South Korean official and a senior U.S. official, said the signature appeared authentic. The senior U.S. official also said that the substance was consistent with the U.S. government’s current understanding of events.

A senior Pakistani official, however, said the letter is “clearly a fabrication,” a claim echoed by the two former Pakistani military officers named in the letter.