As Ottawa recovers from the shock of Tuesday's shooting deaths of four Ottawa transit employees, the city has announced a public memorial service will be held April 18 at the city's Corel Centre.

The huge arena is normally home to the Ottawa Senators hockey team, but has been donated for the service. The service is planned for a Sunday so more transit staff can attend.

Private funerals for the victims' families will be held Friday and Saturday.

Meanwhile, the city's transit headquarters is fielding hundreds of calls since Pierre Lebrun, a former employee of the transit system stormed into a transit garage Tuesday afternoon and began shooting. Six people were hit, four fatally. Lebrun then took his own life.

In tribute to their lost co-workers, transit workers began wearing black ribbons Thursday. On Friday, all Ottawa buses will stop for a moment of silence around 2:45 p.m, about the time Pierre Lebrun started firing Tuesday.

Police say Lebrun was a troubled individual who had had "some difficulties in the work environment." He had been fired from the transit company, OC Transpo, in August 1997 but then was reinstated a month later after a grievance was filed.

Lebrun was said to be a quiet loner who kept to himself. He left a suicide note the day of the shootings explaining his actions, but police would not reveal its contents. The note shows he was upset with what the police call "interactions" at work and clearly showed his intentions.

Ottawa police have said that while Lebrun had a long history of mental health problems, he had no history of violence. The 30-06 hunting rifle used in the shootings was purchased in 1992, following all the legal procedures for that time.

Ottawa's police chief said Wednesday even under Canada's tougher new gun laws, there's nothing that would have stopped Lebrun from owning that rifle.