[AdmSmith]

From NST: “It is also understood that the masterminds had been tracking his movements for about a year to establish his travel pattern, which included flying between Macau, Singapore and Malaysia.

http://www.nst.com.my/news/2017/02/213393/police-identifying-4-n-korea-operatives-video

It is very unlikely that China was unaware of this.

[dfwgator]

At some point, China is going to realize that maintaining the NORK regime just isn’t worth it.

[TigerLikesRooster]

I think N. Koreans had been tracking him for a long time. It is not something which started recently.

There is a report that Kim Jong-un sent Kim Jong-nam a message to return voluntarily but he balked. This could give N. Koreans renewed urgency to eliminate his half-brother. Even if this is not true, Kim Jong-un is facing more challenges lately, and may feel that there should be nobody out there to replace him, however remote the odds are.