Most of us can recognize good and bad, I don't need to determine it. I know of no one who would conclude that what Adam Lanza did was good, and if they do, perhaps we need to lock them away from the rest of society? I have to use human standards to explain things to human beings, otherwise there is no way to comprehend them. You assume, that because I use these human standards, they must apply to God, and that is a false assumption. MY God is an energy force. About the only thing we can relate this to as humans, is electricity. (No, I am not saying electricity is God or God is electricity.) Electricity is a form of energy, we can understand where it comes from, what causes it, and what it is, but we don't understand why it exists in the universe. You don't have to "believe in" electricity, and electricity doesn't care if you "believe in" it or not. MY God is the same.
Your argument is oddly reminiscent of the 'argument' posed by those who crucified Christ. "If your God is so great, why doesn't he save you?" If MY God is omnipresent, he must have been in Adam Lanza that day. But God doesn't conform to humanistic standards, that is simply how we relate God to man, and you are confused by this because, your entire life, you have been inundated by a false concept of God. While he certainly could have been in Adam Lanza, he wasn't. The force consuming Adam Lanza was Evil, not God.