You shouldn't feel guilty about this. There is really nothing you could have done, nothing any of us could have done. Things like this happen in life, because life sucks, but we have to learn to accept that it's not our fault- especially you. Given your circumstance, I see why you're so upset, but honestly this is probably just a coincidence. Don't feel bad, you've done nothing wrong.
R.I.P. those poor victims. God, this is really terrible.