He said security guards then came rushing down the halls, herding them toward the back of the buildings.
"And then we started talking to another woman and she was apparently inside the library of Parliament, saw the fellow, wearing a hoodie, carrying a gun," McKay said, "and then the implications of this start to sink in."
Officials canceled two events in Toronto honoring Pakistani teenager and Nobel laureate Malala Yousafzai, including one in which she was supposed to receive honorary Canadian citizenship. She was shot in the head by a Taliban gunman in 2012 for supporting schooling for girls.
The attack came two days after a recent convert to Islam killed one Canadian soldier and injured another with his car before being shot to death by police.
The killer had been on the radar of federal investigators, who feared he had jihadist ambitions and seized his passport when he tried to travel to Turkey.
Canada had raised its domestic terror threat level from low to medium Tuesday because of what it called "an increase in general chatter from radical Islamist organizations."
In the hours after Wednesday’s attack, police warned people in downtown Ottawa to stay away from windows and rooftops.
Scott Walsh, a construction worker who was in a manhole in front of Parliament Hill, said he heard the shots at the war memorial.
"We’re in construction and we’re used to loud bangs. When people started screaming and running, that’s when I clued, and I saw this guy running" with a gun, he said. "It was intense. I didn’t think it was real. "
He said the gunman had long black hair with a scarf covering the lower half of his face.