Why did North Korea's Kim Jong Un execute his defense minister?

North Korean leader Kim Jong Un is no stranger to the use of brutality to cement his control over the country. Two years ago he executed his uncle and chief deputy, Jang Song Thaek, and a cadre of advisers, for alleged treason.

But his latest move, the reported execution of defense chief Hyon Yong Chol, announced by the South Korean spy agency, raises questions about how firmly he views his grip on power, even as experts believed he was beginning to show some signs of governance.

"This suggests quite the opposite: that he remains insecure in his rule and he's willing to do these kinds of dramatic things to establish his rule," said CBS News Senior National Security Analyst Juan Zarate. "What he's doing is demonstrating with great brutality what insubordination in the current context means. It will mean execution and death and likely exiling if not death of your family members and those who are around you."

South Korea's spy agency, known as NIS, told lawmakers that the people's armed forces minister was executed for sleeping during a meeting and talking back to Kim. He was allegedly killed by anti-aircraft gunfire at a military academy while hundreds watched. NIS has also said that Hyon was "purged," as opposed to executed. The Washington Post says that the agency told local reporters and Korean lawmakers in separate briefings that he had been purged and almost certainly executed publicly. The Post goes on to note that NIS reports are not always accurate.

Zarate said that the latest developments are not only disconcerting for the U.S., but also China. The country has been concerned about North Korea's young leader for some time, especially since the uncle and advisers he killed in 2013 were very close to China.

"The Chinese in recent weeks have been really signaling some concern about North Korea and what's happening internally as well as the acceleration of their nuclear program, and that's unusual for China to be signaling this in some public ways at a time when I think Pyongyang has fallen outside of the complete control of Beijing," Zarate said. "There's a lack of sense of what this leader's really about, even though he was educated in the west, really a lack of sense as to what his guiding principles are, what his state of mind really is."

The U.S. also must often resort to reading events like this one like tea leaves to surmise Kim's state of mind and the state of his regime, Zarate said. He noted that former NBA star Dennis Rodman - who has visited North Korea multiple times - has had more contact with Kim than any other official of the U.S. government.

  • Rebecca Kaplan

    Rebecca Kaplan is a political reporter for CBSNews.com.