This is tragic and I believe that it could have happened to any one of us. We are all human (not robots, yet!) and for what ever reason, we all make mistakes.
At this stage nobody really knows why this happened. Pilots, ATC etc. It's all guess work. Usually there are a combination of events that lead up to this kind of incident.
Lets wait until the report comes out before pointing fingers and even then, I hope, that instead of pointing fingers, we can all learn a thing or two, regardless of whos jobs whos and try to avoid a similar result in the future.
In the mean time we could all see it as a bit of a wake up call!