— Ottawa police say they receive reports of a Canadian honour guard shot at the National War Memorial.
— Reporter Josh Wingrove of the Globe and Mail tweets that he hears gunfire inside Parliament's Centre Block building. In a subsequent tweet two minutes later, he reports hearing "dozens" of shots and sees a body on the ground outside the Library of Parliament.
— As word of the shootings goes viral online and dominates TV newscasts in Canada and around the world, the RCMP tweets out its first statement asking the public to stay away from Parliament Hill "due to ongoing police incident." The public is later asked "to stay away from windows and off roofs" in downtown Ottawa.
11 a.m. - 2 p.m.
— Ottawa police announce on Twitter that they have closed all their stations and won't offer any services to the public while the investigation into the shootings continues.
— Soon after, a statement says officers are "investigating several shooting incidents in downtown Ottawa."
— Politicians, journalists and staff on Parliament Hill and people in downtown Ottawa are largely forced into lockdowns or evacuated from the area as growing numbers of police officers search for one or more suspects.
— An NHL game between the Ottawa Senators and the Toronto Maple Leafs scheduled for Wednesday night in Ottawa is postponed.
— The Quebec national assembly and the New Brunswick legislature close outright while some other provincial government buildings either restrict public access or beef up security.
— The U.S. State Department says it's limiting movement of personnel at the U.S. Embassy in Ottawa, which is located near Parliament Hill.
— Ottawa police confirm the soldier is dead, as is the gunman. "This is an ongoing police operation and there is no one in custody at this time," police say. An earlier report of an incident at the Rideau Centre is retracted as incorrect.
2 p.m. - 4 p.m.
— At a press conference, police won't say whether they believe a second shooter was involved and still on the run. They say the investigation continues and ask Ottawa residents to remain on the watch for anything suspicious.
— The Prime Minister's Office releases a statement with Stephen Harper calling the shootings a "despicable attack."
— The White House summarizes a call between U.S. President Barack Obama and Harper. Obama condemned the "outrageous attacks" and offered assistance in responding to the shootings.
— Some buildings in Ottawa's downtown core, including the Rideau Centre, have their lockdowns lifted and people are allowed to go home.
— Ottawa police say its "safety perimeter" has been reduced in size. Residents inside the area are still asked to stay indoors until further notice.