The gunman behind the shooting on Parliament Hill took a tour of the House of Commons and the Senate less than three weeks before he opened fire on Cpl. Nathan Cirillo and was later gunned down outside the parliamentary library.

Multiple sources told CBC News that Michael Zehaf-Bibeau can be seen taking a public tour of Parliament's Centre Block on Oct. 4. Security cameras caught a clear image of Zehaf-Bibeau leaving the Senate chamber as part of a tour that day.

Zehaf-Bibeau was killed in a firefight with Sergeant-at-Arms Kevin Vickers and other security forces in Parliament's Hall of Honour on Oct. 22, mere minutes after shooting Cirillo from behind while the corporal stood ceremonial guard over the tomb of the unknown soldier at Ottawa's National War Memorial.

The sources, who asked not to be identified because they were unauthorized to speak publicly about the investigation into the shooting, told CBC News that the video suggests Zehaf-Bibeau's assault was planned and premeditated.

The Ottawa shooting led to an all-day lockdown of Parliament and several downtown buildings while police investigated whether there was more than one gunman.

The Hill incident came two days after another soldier, Warrant Officer Patrice Vincent, was run down in a deliberate hit-and-run by Martin Couture-Rouleau in St-Jean-sur-Richelieu, Que.

The events led to an increase in security at Remembrance Day ceremonies in the capital and across the country.