When the smoke cleared, von Brunn was critically wounded.

"Two other . . . armed security officers opened fire with their service revolvers," the company said. "The intruder was hit at once" and wounded.

Johns died at George Washington University Hospital.

"There are no words to express our grief and shock over these events," the museum said in a statement, describing Johns as "an outstanding colleague who greeted us every day with a smile."

Johns, a 1988 graduate of Crosslands High School in Temple Hills, lived in an apartment in the Temple Hills area. Friends said he had a son.

"It's a heavy loss," said Assane Faye, the Washington district director of the Security, Police and Fire Professionals of America.

Faye said that during contract negotiations with Wackenhut two years ago, the union pressed for company-issued protective vests. Although Wackenhut seemed open to the idea, vests have not been issued, Faye said.