That's horrible, it makes me thankful that guns are banned here in China and schools have reasonable security.
Here's a link to the China related article:
(you need an account to see links)
At least no one died, if it was a gun, I fear the result would be much worse. Though thankfully here there is security who would have reacted pretty fast to an unknown trying to enter the school. Schools here have big walls to keep unwanted people out.