Here is my opinion. The problem with the world today is that everyone has become selfish and expects the world to bend to their own expectations. The problem, I believe, is that parents have not taught their children that life will always be a series of ups and downs. Sometimes we are on top of the world and everything goes our way. And there are times when everything in the world seems to be against us and we cannot win.
Rabbi Nachman of Breslov would teach his students that depression is natural but with the proper outlook a person can deal with the negative parts of life while retaining his inner joy. I have been studying a lot of Mussar {Character Development} and I have learned that everyone deals with set-backs. Some people who learn are able to deal with these negative events in their life.
I have read recently that the shooter in this case suffered from 'depression'. While there are medical conditions which can bring on depression I believe that even those who suffer from these conditions can change their nature. I have actually seen it happen. I look at myself who struggles daily with many problems which would cause others to loose faith.
It is terrible that evil like this exists. It seems that every day we read about people snapping and killing themselves and their families. The brutal nature of mankind stems from our animal souls which compete with our G-dlike souls for prominence. The victims are innocent and do not deserve their fate, but they will be rewarded for their suffering. As my brother was a victim I know he is rewarded in the next world. The free-will of the perpetrator, unfortunately, is of utmost importance to bring this world to its desired goal.
My prayers go out to all the victims who suffer at the hands of this worldly evil. I pray for protection for all who have faith and walk in the ways of the wise.