I think you're being too hard on yourself. I live in Boston and have friends who were in very real danger, and I still had that same thought go through my head. On the merits of the the thought, we should not accord much weight to the "it's too soon!" line of thinking. Nor is the tragedy of a death proportional to its media coverage. So you aren't being monstrous.

But more importantly, having a thought you aren't proud of is no mortal sin, nor is publishing it honestly on the internet. You're supposed to feel conflicted and confused; something bad happened and we're all going to have a wide range emotionally-charged responses.