Story highlights North Korean defector claims Kim Jong Un ordered aunt to be killed

Park says Kim wanted to silence Kim Kyong Hui after she angrily complained about her husband's execution

Jang Song Thaek was executed after allegedly trying to topple the regime

Seoul, South Korea (CNN) Mr. Park shifts uncomfortably in his seat. As one of the most senior North Korean officials to ever defect, he was preparing to tell the ugly truth about the regime he served faithfully for decades.

This is not his real name; he wants his identity hidden for fear of retribution against friends and family still in Pyongyang. It's not surprising when you hear what he has to say.

His first allegation is shocking. He claims North Korean leader Kim Jong Un ordered his own aunt, a blood relative, to be poisoned.

"On May 5th or 6th of last year," says Park. "Kim Jong Un ordered his aunt, Kim Kyong Hui, to be killed. Only his bodyguard unit, Unit 974, knew this -- now senior officials also know she was poisoned."

Park says Kim Jong Un wanted to silence his aunt, who complained angrily for months after her husband and presumed No.2 in the country, Jang Song Thaek, was killed in December 2013.

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