He walked in with a RIFLE!
Of course had there only been some gun control law that could have stopped him, or maybe a restraining order based perhaps on...
"In 1983, he was convicted of attempting to kidnap members of the Federal Reserve Board. He was arrested two years earlier outside the room where the board was meeting, carrying a revolver, knife and sawed-off shotgun. At the time, police said Von Brunn wanted to take the members hostage because of high interest rates and the nation's economic difficulties."
... then this, of course, could not have happened he would have been afraid of the judge.
I feel sorry for the family of the security guard who died, he should have fired a little bit faster.
Glad your daughter is safe ... was she actually at the museum or just in DC?