The very short story is that the market is crashing. The government is panicking because it unwisely tied its reputation to a rising market. It compounded its error by trying all kinds of measures to stop the fall--all of which have failed--which have damaged their reputation even more because it has made it clear that the authorities have no idea what they are doing.
Millions of people have lost money speculating in this market. Prices are falling so fast that most of the stocks traded on the Shanghai and Shenzhen exchanges have had their trading suspended, either because their prices have fallen to their daily limits or because their companies have requested that their stocks be suspended. At the rate things are going, there won't be any stocks left to trade at all by the end of the week.
It's an amazing spectacle. The authorities look powerless and incompetent. Mostly it's something the Chinese government did to themselves. And it was all so predictable: it is the nature of market bubbles to burst even faster than they inflate.