On my Thursday, Malaysian authorities arrested the second of two women in connection with the death Monday of Kim Jong Nam, once in line to lead the North Korean regime.

Kim, the elder half-brother of leader Kim Jong Un, died on his way to a hospital after an unidentified woman covered his face with a cloth containing an agent of some sort.

North Korean diplomats unsuccessfully tried to prevent an autopsy and obtain the return of Kim Jong Nam’s body.

The assassination, which took place in the budget terminal of Kuala Lumpur International Airport, suggests the North Korean regime is unstable and its leader is desperate.

Jong Nam was the eldest acknowledged son of Kim Jong Il, the second Kim family member to rule the Democratic People’s Republic of Korea. Jong Nam fell out of favor as his father’s heir in 2001, when he was detained trying to enter Japan on a fake Dominican passport, ostensibly to visit Disneyland.

Kim Jong Il, after his 2008 stroke, began to train Jong Un as his successor. The young Kim in December 2011 became the third from his family to rule when his father died of a heart attack.

Jong Nam in recent years lived under Chinese protection. Beijing apparently wanted a Kim in reserve to possibly serve as a China-friendly leader of a successor regime in Pyongyang. Jong Nam, often called a playboy, appeared to harbor no desire to do so and exhibited little aptitude for such a demanding role.

In reality, Jong Nam posed virtually no threat to his half-brother’s rule, but that did not mean Jong Un did not try to kill him. There was also an assassination attempt in 2012.

Kim Jong Un, unfortunately, is now known for blood lust. He has ordered the execution of 340 officials according to one recent count. Some Korea watchers believe that, once those sent to camps are included, the total is closer to 500.

When viewed in this light, the killing of one more individual, his half-brother, looks to be unexceptional. Yet ordering a hit on a Kim, in a society where family members were once considered divine and where regime legitimacy rests on bloodline, is an especially heinous act.

It is also a desperate one. The execution of a family member can intimidate others in the short term, but it erodes support and undermines regime credibility. The murder could even be interpreted as a last resort.

It is so risky that it might also be Kim Jong Un’s last mistake. “At some point, that symbiotic balance of power, that invisible balance of power between the tyrant and his sycophants, that will be broken,” Lee Sung-Yoon of Tufts University’s Fletcher School of Law and Diplomacy told radio-show host John Batchelor on Wednesday night. “I see his own grim fate in the face of his half-brother.”

The killing of his Nam Jong is not the only sign of instability in Pyongyang this month. Two weeks ago, for instance, the world learned of the demotion of the minister of state security, General Kim Won Hong. On Sunday, the chief of North Korea’s strategic missile forces did not witness the launch of the Pukguksong-2 intermediate-range missile, indicating instability at the top of the Korean People’s Army.

Whether Kim Jong Un is deeply insecure or suffering from a “delusional disorder”—the diagnosis of South Korea’s National Intelligence Service—the international community faces a North Korean supremo who now exhibits a low threshold for risk, largely because he feels he has so little to lose.

Kim has long-range missiles—three that can reach the western U.S.—and a stockpile of enough plutonium and uranium to fashion about 16 to 20 warheads. His technicians have almost certainly learned how to mate a nuclear warhead to his intermediate-range missiles and within, say, four years will have mastered the ability to strap on nukes to his intercontinental-range missiles as well.

Few think the Kimster would ever launch in anger because missiles have “return addresses”—in other words, their launch sites can be traced and target countries can retaliate. Yet to bolster legitimacy, he might try something unthinkable, especially if he believes he can get away with it because of the political disarray—the impeachment crisis—in Seoul.

And if Kim creates a confrontation that turns out badly for him and thinks he will die anyway, he might decide to take everyone else with him. “One is pleased to see the bugs die in a fire even though one’s house is burned down,” Kim Il Sung reportedly told his son, Kim Jong Il.

Kim Jong Il expressed the same sentiment this way: “If we lose, I will destroy the world.”

Kim Jong Un now has the arsenal to do just that. So call his murderous family drama “Macbeth with Nukes.”