HOW TO RESPOND TO COMMUNAL CALAMITIES - Rambam, Hilchos Taanis 1:1-3, Mishna Berura 576:1

Maimonidies - the Rambam writes that when the Jewish people are experiencing such tragic situations, the Torah obligates us to cry out to God and sound trumpets to arouse us to repentance (Bamidbar 10:9). If we realize that our own actions are at the root of our difficulties, we will learn to mend our ways and cause the harsh decree to be rescinded. If we don't follow this path, and instead relate to what is happening as mere coincidence, the problems will simply increase (Rambam, Hilchos Taanis 1:1-3, Mishna Berura 576:1).