Why did so many people die in the 5. 12 earthquake?

Wenchuan earthquake occurred on 12, and in May 2008 14: 28: 35, which was my most worrying day. Although I didn't personally feel the earthquake, I can feel how painful it is for us. The magnitude of the Wenchuan earthquake was 8.0 on the Richter scale. The first report was 7.9, and later it was changed to 8.0. We were killed. So who are the most casualties? Let me tell you, because it happened in the afternoon 14: 28, which is usually the time for students to attend classes and go to work. Because of the sudden earthquake, the vibration lasted only a few tens of seconds, and students and staff working in high-rise schools generally had no chance to run downstairs. There is a place where children in kindergarten are taking a nap, and those old people with inconvenient legs and feet have no chance to go outdoors at all. This is to some extent.