This will be a quick answer and I don't intend to be glib. God was simply not invited. In 1947 the Supreme Court reversed course of the previous 150 years of rulings and ruled basically that church and state should be separate. It's not in our constitution but when they married the 14th amendment with the 1st amendment, which by the way was 1st for a good reason, we got a reverse course of action that opened the door to many more rulings that just left God out of public life. We are were, a country set up on Biblical ideals.
So this being a public event at the movie theatre, God was simply not invited and in fact was prohibited from being there. What I mean is over a long period of time Americans have demanded to keep God in a box at churches on Sundays only and this is simply a result of that policy. Then suddenly the news media questions why God wasn't there? We can't have it both ways... having our cake and eating it too. It just doesn't work like that.
If you listen to many of the victims speak out, you hear those who were praying and then in the aftermath you see God move, once He is invited in. He is the Lover of our souls. Jehovah Shammah- The Lord is there. Until we believers get more vocal with and bold in our public displays of love for our Father, we can look forward to much more carnage no matter how much security man places about.
More detail on this subject to follow soon.