Stephen Tyrone Johns died `` heroically in the line of duty , '' museum says . Suspect is 88-year-old white supremacist , law enforcement officials say . Score: 6 Security guard and shooter were wounded in exchange of gunfire , police say .
Stephen Tyrone Johns died `` heroically in the line of duty , '' museum says . Suspect is 88-year-old white supremacist , law enforcement officials say . Man with `` long gun '' entered museum , fired at guard , police spokesman says . Security guard and shooter were wounded in exchange of gunfire , police say .