I discussed mass murder with a woman a few days ago. She said that society is also responsible for mass murders. However, I don't like this opinion. Of course, there are various problems in all countries, but there isn't any excuse that would support the ideas that we allow mass murder. She seemed to shift the responsibility of mass murderers to society, as if to say "Society creates mass murderers."
There are many people who live without committing a serious crime in the same society, even if they have frustrations with their societies. I think most mass murderers attribute their unfortunate conditions to society and others, not to themselves. This is very selfish. People who killed many people must be responsible for their actions. Then, we should investigate their backgrounds of their actions so that mass murder will not happen again.