A security guard was pronounced dead at the GW Hospital Wednesday after an 88-year-old white supremacist opened fire at the Holocaust Memorial Museum.

The suspected gunman, James von Brunn, walked into the museum with a “long gun” shortly after 1 p.m. on June 10, according to police. He immediately shot Stephen Tyrone Johns, 39, a special police officer working on the first floor of the museum, police said.

Von Brunn suffered injuries after two officers guarding the front entrance returned fire. Both injured men were transported to the GW Hospital by D.C. Fire and Emergency Medical Services, where Johns, a Maryland resident, was pronounced dead, and von Brunn was admitted in critical condition.

Nicole Pokryfka, a spokeswoman for the hospital confirmed that two gunshot victims from the Holocaust Museum were brought in that afternoon.

The Holocaust Memorial Museum announced it will be closed for June 11 and flags will be flown at half-mast in honor of Johns.

“Officer Stephen Tyrone Johns died heroically in the line of duty today,” a statement released by the museum said. “There are no words to express our grief and shock over these events. He served on the Museum’s security staff for six years. Our thoughts and prayers go out to Officer Johns’ family.”

The Holocaust Memorial Museum is located near the National Mall in Southwest D.C. According to the museum’s Web site, nearly 30 million people have visited the museum since it opened in 1993.