When violence strikes innocent people close to home, you can expect religious leaders to immediately scramble to explain how their god can allow such things to happen. Some, like Bryan Fischer and Mike Huckabee, have suggested that god is punishing people for excluding religion from schools. Others are more aware that such a message it not particularly good public relations for their god and try to square the events with a god who is good and not easily irked into fits of violence.
Cathy Lynn Grossman rounds up some of those reactions. The usual suspects are trotted out, such as that this is the price that we pay for god having given us the gift of free will, that some people will necessarily abuse it, that there can be no good without the bad, and so on. Others have said that we have to trust that despite all appearances to the contrary, there is some divine and good plan unfolding and we just have to wait and see what it is.
Theodicy is undoubtedly the Achilles heel of religion. There is simply no way to sensibly explain suffering while postulating a good god and each such atrocity reminds people of that fact.