Kim Jong-un was living in China and was under China's protection. They took a dim view of North Korea murdering him, and this fallout is almost certainly due to that.
Bullcrap. Trump certainly has told China that they need to deal with North Korea if they want to keep any of their trade situation with us intact. North Korea probably offed that brother because they knew the threat from China was increasing.
It would be nice if the Chinese would kill him but they did nothing when he had a South Korean naval ship sunk without warning or cause. If they do not kill him I predict a nuclear attack somewhere like in Israel from weapons supplied to the Iranians or the USA by this guy.