We never will know the exact cheshbon of why these tragedies occur but we do know that we must do that teshuva is the antidote to tzar. So each of us has an obligation to think into where we are lacking and to make a plan to rectify our weakness in Avodas Hashem. If we all take these events as personal which they are and then do the required soul searching, we can bring about a better shemira for the klal.