After a man was killed by a shell fired across the border from Ukraine into a Russian town, Moscow told Kiev Sunday there will be "irreversible consequences." There have been cross-border shootings before, however this looks like the first time Russia has reported a fatality. The three-month conflict has killed hundreds in Ukraine. Kiev, meanwhile, denies that Ukrainian forces fired across the border, and said it could have been rebels trying to get Moscow to intervene on their side. Russia sent Ukraine a note in response, saying the shell was "an aggressive act by the Ukrainian side against sovereign Russian territory and the citizens of the Russian Federation."