(Portland, OR)  --  An investigation is ongoing into the officer-involved shooting death of a suspect who was allegedly holding a woman at knifepoint while threatening to detonate an explosive device in the Pearl District.  The Portland Police Bureau says officers responded to The Lovejoy building yesterday morning for the incident inside the building's stairwell.  Police say responding officers found the man holding a woman hostage in the stairwell.  Officers tried to speak to the man before eventually opening fire, killing him.  The woman was hospitalized for injuries but is expected to be OK.  Police say they were not able to find any explosive devices on the premises.