China finds itself in a difficult spot. If North Korea irrupts into chaos. Then tens of thousands of North Korean refugees may flow across the Chinese border. China does not want this.
Yet China holds the cards on North Korea. Other nations namely the US and South Korea may be unwilling to take military action for not having a clear idea of how China will respond.
However to continue to do nothing only encourages this crazy regime to think that they can continue attacks. If this is allowed eventually American forces on the DMZ will come under attack. If large numbers are killed this will precipitate an attack by US forces and the situation will erupt back into full scale war.
China needs to do what Russia did to Cuba. Cut it of financially and a blockade of North Korea by the Five Permanent members of the UN Security Council must take place. This regime has to be toppled for the good of the rest of the civilized world. See NATO to Run Security In Afghanistan For Four More Years. At chucksview.com