MP Maurice Vellacott describes chaotic scene on Parliament Hill

Maurice Vellacott was preparing to give a tour of Parliament Hill's East Block when he heard a loud bang.

At first, the MP for Saskatoon-Wanuskewin thought it was a faulty air-conditioning unit or a minor earthquake.

"But at the point when you see officers running in with their side arms pulled and so on, then you know there's something pretty serious happening," he said.

"They're rushing up, with sidearms out and up the steps of the parliament building, so then we knew it was a very serious thing, whatever happened."

What he heard were gunshots fired at a soldier standing guard at the National War Memorial. The memorial is located across the street from the building Vellacott was giving a tour of to home schooled children.

Over the course of 18 years in Parliament, he said he's seen a tightening of security, but never thought something like this would happen.

"I mean, you always know, that there's that possibility, being the centre of government here," he said.

"It's a pretty concerning thing, I mean there are crazy people out there, you don't know what to make of it in terms of if it's a concerted plot, if it's radicalized people, what exactly it is. Somebody's got some beef, some gripe or whatever."

He said the group of about 30 people on the tour with him were all right and in a safe place.