Michael Zehaf-Bibeau was shot dead on Parliament Hill just minutes after he shot Cpl. Nathan Cirillo at the National War Memorial on Wednesday morning.
CBC News has learned from Mission residents and police sources that Zehaf-Bibeau had been staying at the homeless shelter for about a week to two weeks. Shelter resident John Clothier told the CBC's Judy Trinh that many residents had seen him at the shelter.
"I overheard him trying to buy a car ... a small car, because his car had a misfire, he said," Clothier recalled Thursday. "He wanted to buy a car, desperately, and he was trying to get help from everybody in here to get a car.
"People were trying to help him, but we didn't understand what he was up to."
Clothier described Zehaf-Bibeau's as "very bizarre," but not more bizarre than some other shelter residents.
"We did know one thing, that he was saying things like we should be praying five times a day because the end of the world is coming, and stuff like that," Clothier said. "He was right, and everybody else was wrong. I didn't understand what he was talking about."
Police arrived at the mission early Wednesday evening, Clothier said, to collect Zehaf-Bibeau's belongings. Clothier said investigators also spent "quite a while" inside the Ottawa Mission's computer room.
"A lot of people are kind of scared that we're harbouring terrorists in our shelters now. It's just scary. I've been in the shelter system for almost 12 years," Clothier said.
The Ottawa Mission's executive director, Peter Tilley, said Thursday that the organization has been working closely with police, but that he can't confirm or deny whether Zehaf-Bibeau stayed there, citing privacy concerns.
"We've been working in partnership with the Ottawa police and the RCMP, trying to get a handle on everything that's been happening here," Tilley said.
"We can't confirm or deny out of respect for the privacy of our clientele or anybody who happens to stay here. ... Many people stay here at the Ottawa Mission."