Peter Bergen : The Washington Navy Yard shootings not an isolated incident . There has been a string of cases of veterans and young people attacking military targets . Bergen says it 's good that Defense Department is fixing flaws in security . Bergen : One issue that slipped through the cracks was status of security .
Peter Bergen : The Washington Navy Yard shootings not an isolated case . There has been a string of cases of veterans and service people attacking military targets . Bergen says it 's good that Defense Department is reviewing flaws in security . Bergen : One issue that slipped through the cracks was status of contractors .