What can we and society do in order to prevent mass murder?

I feel that mass murder has been increasing recently, especially in the U.S. I often hear we must take measures against it such as gun control, mental care, prohibiting violent movies and video games and so on. However, they seem not to work so far. Even if we have strict gun control,  murderers can kill many people in other ways. On the other day in Japan, a murderer killed 35 people by setting fire on spreaded gasoline. It is impossible to notice and treat all people's mental illnesses who may commit mass murder. Even if we prohibit violent movies and video games, they would keep existing illegally.

 

Nothing can be done about it? I think that the most important thing is to know the importance of life. If they kill people, the people are not alive. The victim's family and friends will feel deep sorrow and anger with the assaulters. I think mass murderers can't understand their sorrow. How can we tell people about the importance of life? Especially to people who may commit mass murder, though it is very difficult to find them, Are there any effective measures against mass murder? What can we and society do in order to prevent mass murder?

 

Corrected

What can we as individuals and as a society do in order to prevent mass murder?

I feel that mass murder has been increasing recently, especially in the U.S. I often hear we must take measures against it such as gun control, mental health care, prohibiting violent movies and video games and so on. However, they seem not to be working so far. Even if we have strict gun control,  murderers can kill many people in other ways. On the other day in Japan, a murderer killed 35 people by setting fire to some spread out gasoline. It is impossible to notice and treat the mental illnesses of all people who may commit mass murder. Even if we prohibit violent movies and video games, they would keep existing illegally.

 

Nothing can be done about it? I think that the most important thing is to know the importance of life. If they kill people, those people are no longer alive. The victim's family and friends will feel deep sorrow, and anger for the assaulters. I think mass murderers can't understand their sorrow. How can we tell people about the importance of life? Especially to people who may commit mass murder, though it is very difficult to find them, Are there any effective measures against mass murder? What can we, as individuals and as a society, do in order to prevent mass murder?