Unless terrorists wanted to kill a handful of pedestrians, the National War Memorial consists of a cenotaph, the tomb of the unknown soldier, some statues, and flowers. I don't think it has any strategic value as a terror target.
I sympathize with a desire to arm soldiers standing guard, but it probably never honestly occurred to anyone that the honour guard at the war memorial would ever have to shoot at anyone. The worst thing that's happened there before was a drunk teen who pissed on the cenotaph a few years ago on Canada Day.
However, it has caused enough alarm, that the US government has posted more armed guards at the Tomb of the Unknowns, at what CNN is calling “hallowed ground.”
It appears the jihadist direct to kill soldiers, also means to kill the soldiers around fallen soliders.
Also, a producer from one of your news stations reported to CNN that the gunman took off on foot from the war memorial to where the office is of the prime minister. He then jumped over a barricade ( another jumper!) and commandeered a car in that secured area, until he got to the Center Block, which I understand is the main building for parliament.
I can only think that he was so pumped with adrenalin and bravado after his first successful hit, that he made that incredible dash to where the caucus was being held, to get even greater notoriety.
I think the soldier on guard was shot point blank, and four shots were fired.