I am really sorry for those lives lost, but this kind of attacks or killings are not something new but as long as we live in a world where every one just trying to have all for themselves then comes chaos and always will be a special group of people that always go to the extremes.
One thing is not certain and clear which is why these people do what they did? what is to gain?
This world is a place when you can do what ever you want because we all have free will but when we never face any consequences then we continue to do what the hell ever we want. you need to find the reason behind these attacks which in my arrogant opinion is our governments.