Update 4:20 P.M.
D.C. police say a Holocaust Museum guard, Stephen Tyrone Johns, and the alleged shooter, James von Brunn, were rushed to George Washington University Hospital.
Police have now confirmed that Johns has died.
Massachusetts teen charged with involuntary manslaughter; authorities say she "strongly influenced" high school friend to kill himself
New evidence may point to the innocence of a caregiver convicted in a child's murder -- so why did she confess?