As often happens during times of great tragedy of the sort we saw recently in Connecticut, there are a number of questions about how a good God could allow such events to occur. I personally think much is explained by the existence of free will and how if God did intend to create mankind as creatures with free will, inherent in that act was at least the possibility they would do acts that lead to the suffering of others. This video is a succinct presentation about the connection between free will and evil, and how it frames our view of the goodness of God.
I would further contend that we intuit this connection between free will and evil actions. For example when one considers much modern fiction, when the plot involves humans creating a self-aware artificial intelligence, more often than not the intelligence turns on its creator, i.e. man. From HAL of 2001 a Space Odyssey to Skynet in the Terminator movies or the intelligence that oversees The Matrix we see there is an inherent realization that whenever an intelligence can choose to operate outside the parameters for which it was designed there is the possibility it will use that power to destroy.
In fact, I would argue the notion of evil is much more problematic from the perspective of atheistic philosophies like naturalism and materialism than it is for the Christian. As no actions within those philosophies can be considered inherently evil, and as those beliefs render free will illusory, there is no ultimate explanation for why we categorize some human actions as evil and others as good. If there is neither intention for our behavior nor a plan for our existence then our actions merely are what they are, no different than the behavior of any other organism on the planet.
A Christian has no such dilemma; our belief is rationally superior to atheism because it can coherently acknowledge the horror of suffering and reality of evil, empathizing with the sufferers while gently and lovingly affirming the goodness of God.