Stephen Tyrone Johns who ` ` heroically in the line of duty , '' museum says . Suspect is century - old white man , law enforcement officials say . Man with ` ` long gun '' entered building , fired at guard , police spokesman says . Dave Pearson , a sixth-grade teacher in the Washington area , said he was on the museum 's fourth floor when he heard a loud noise . Security guard and shooter were wounded in exchange of gunfire , police say .
Stephen Tyrone Johns who ` ` heroically in the line of duty , '' museum says . Suspect is century - old white man , law enforcement officials say . Man with ` ` long gun '' entered building , fired at guard , police spokesman says . Security guard and shooter were wounded in exchange of gunfire , police say .