Tragedy in Virginia University

Since last week people have been talking about what happened in Virginia University. A student killed thirty three people, including himself. There is much speculation about American Society.
It began when a young man got in a class room and killed two people. After that, the killer walked to another building to kill the rest of the people. That list included students and teachers. I heard that when he tried to go in to one of the classes, a teacher tried to keep the door closed to help students jump from the window. It is amazing how those people were assassinated very close and very fast.
The students are dismayed, this is the worst attack of its kind that has ever happened here. Also the students and their families dont feel safe. I think they are scare to come back.
I really dont know the rason, it could be a cultural problem. Similar crimes happen in New York a lot.