(Portland, OR)  --  Police say officers arrested six people during a riot that followed a peaceful day of May Day demonstrations in Portland.  The Portland Police Bureau says one group demonstrated at Portland City Hall, where they broke windows and spray painted graffiti.  A second group demonstrated outside of the ICE building in south Portland.  Police say one man pulled a knife on officers.  Police arrested 22-year-old Jeremiah Day for menacing officers with a knife.  Charges against the other five people include riot and criminal mischief.