Horrible. Poland has been through so much pain, they don't deserve any more.
That said, I hope the international community looks into the causes of this disaster, and not just Russia... This wouldn't be the first time "accidents" have happened to people Russia didn't like...
http://en.wikipedia.org/wiki/Poisoni...der_Litvinenko
95% chance this was just a horrible mishap, but I don't put much past Putin...