Even as a follower of Jesus, I find myself thinking on such things in a carnal way. In a psychological way. Perhaps because I'm a pschologist by education, and a logical thinking, left-brained, pragmatist by nature, I do this. However for all we know, and for how much more advanced we humans have become (in worldly terms), we have not escaped our nature. We are not protected from man's terrible nature. We are not immune to the effects of man's wickedness in a fallen world. The shooter is a relatively extreme manifestation of this wickedness.
I truly believe in an almighty, sovereign, loving, just, and empathetic God. Is God all powerful? Powerful enough to stop suffering and evil acts like those committed in D.C. yesterday? I would say absolutely. Why doesn't he then? Well, simply put, he does what does and allows what he allows all according to His sovereign will. How crappy would it be if God acted according to my selfish will and my selfish desires? He's allowed me to suffer terrible loss, tragedy, financial burden, stress, shame and pain on high levels. It makes him no less the sovereign creator of the Universe and sustainer of all things. I have confidence that in the end, my experiences and hardships work for my good and His glory.
I want just put this out there quickly: Suffering exists because this world is broken. God is not broken. Man at his core is wicked. Some arguably are more wicked than others. God however, is not wicked at all. Some angry man can put a bullet in the back of my head tonight. It would not make God any less glorious or perfect. The wicked things of this world draw me even closer and dependent on Jesus for every "next" breath I take. If the work Jesus needs me to do here on Earth is finished, and he lets a nutjob take me out, then I'm ready to go home. Times like this make me want to press into God more, not doubt his goodness. My prayer is that his presence can be felt in a tangible way for all the broken hearted people in D.C., the US, and the world.