I’m going to go out on a limb here and say that Kim Jong-un did it..
So now who is the next heir to the North Korean throne? I wouldn’t want to be that person.
The Norks are brutal.
They did awful things on the battlefield during the Korean War.
After the war they kept on doing crazy things like hacking an American solider to death guarding at the ‘truce village’ at Panmunjom.
In 1987 two NK agents planted a bomb on a South Korean airliner destroying it and killing over 100 people as the plane approached Bangkok.
When they were about to be caught in the UAE, the agents took cyanide.
Those and plenty of other incidents from the NK regime.