– While much remains mysterious about the assassination of Kim Jong Un’s half-brother in Malaysia this week, this much is clear: Nearly all of the North Korean dictator’s potential rivals are now dead.

In the nation’s patriarchal dynasty, Kim Jong Nam, 45, represented a possible alternative if elites ever moved to oust Kim Jong Un, 33. The older brother had lived outside North Korea for years, frequenting casinos in Macau and occasionally criticizing his younger sibling’s regime. His only other brother, Kim Jong Chol, 35, isn’t seen as a main threat to usurp power.

Malaysian police arrested a female suspect carrying Vietnamese travel documents on Wednesday, and they are looking for others who may be involved. While there’s no evidence yet linking the murder to Kim Jong Un, South Korean lawmakers and observers of the secretive regime see him as the clear winner.

“Did Kim Jong Un order the assassination? Yes, almost certainly,” said Van Jackson, a former Department of Defense adviser who now teaches at the Daniel K. Inouye Asia-Pacific Center for Security Studies in Honolulu. “He lives a nightmare version of Machiavellian court politics every day, and bloodline is still the strongest claim to legitimate rule in North Korea: Eliminating potential centers of power is cold but shrewd.”

The murder has raised questions about the stability of Kim Jong Un’s regime as he seeks the ability to strike the U.S. and other threats with nuclear weapons. President Donald Trump has vowed to deal with the threat “strongly.”

Pressuring Kim without triggering the country’s collapse isn’t easy. The Kim family dynasty has ruled North Korea for three generations since its founding after World War II, when the Soviet Union and the U.S. divided up control of the Korean Peninsula. It has built up one of the world’s most vigorous personality cults.

The birthdays of founder Kim Il Sung and his son Kim Jong Il are the biggest national holidays in North Korea. The country has held mass propaganda events to praise the Kim family. Those caught denigrating the country’s leaders can be either sent to prison camps or put to death.

Kim Jong Un has routinely conducted purges to consolidate his grip on power, a practice also employed by his father and grandfather. Although there is no great indication that he faces the threat of a coup, that prospect looks even more remote with Kim Jong Nam gone.

The male-dominated leadership structure all but rules out Kim Yo Jong, Kim Jong Un’s sister, as a successor.