Thankfully it appears that there are no fatalities but as to the reason, I am sorry I cannot help you there as I have no idea what goes on in the mind of a fanatical religitard.
Getting to the point where I don't even want to look. Hard to balance the desire to stay informed with trying to stave off despair from seeing yet more reminders of humanity at its worst.
Because it's an easy cosmopolitan target and those that do these things can just blend in with the crowds.....it's also one of the worlds most important city's business wise and always in the publics eye world wide.......