The U.S. and Ukraine are accusing Russia of launching artillery attacks on Ukrainian troops from Russian soil and preparing to move more heavy weapons over the border. Over the past two weeks, half a dozen artillery barrages have already been fired from southern Russia. David Martin reports.
U.S. officials: Russia has fired into Ukraine
What to Read Next
'The Walking Dead' Midseason Finale: Will These Questions Get Answers or Cliffhangers?