Our final concern must not be how many died in tornadoes or school shootings, but how many souls were lost. How many fell into eternal damnation in those tragedies. It is in this light we can begin to understand why miracles occur and why some are saved from a particular catastrophe and some are not. We are all sinners and ultimately in terms of this world the same fate awaits us all. God does have a purpose and a will for us and that basically is that we will all repent, i.e., turn to him and live.
Violence exists because of Sin.
It is not necessarily possible or even desirable to connect a specific sin to an event. To do so misses the point. Miracles occur that we might see that faith is not in vain. If miracles were common place we would not recognize them when they occurred. They are rare that we might see God's hand in action and know that his promises to us are true.