A gunman shot one of the two soldiers standing guard at the Canadian War Memorial in Ottawa and was then chased by police into the main parliament building, where at least 30 more shots were heard, according to media and eyewitness reports.
Other soldiers doing drills nearby ran to help the fallen soldier and eyewitnesses said the person shot was a soldier because of the ceremonial uniform the he was wearing.
The wounded soldier was taken into an ambulance where medical personnel could be seen giving him cardio-pulmonary resuscitation.
Parliament was locked down and Prime Minister Stephen Harper had left the building safely as police converged on the area.
There were "several shooting incidents in downtown Ottawa" on Wednesday morning, police said on Twitter. "Incidents occurred at National War Memorial, near the Rideau Centre and Parliament Hill." All Ottawa police buildings remain on lockdown and are closed to the public, police also said on Twitter.
CBC News said in a tweeted news alert that more shots were fired near parliament and the gunman was still at large.
Police and tactical teams had converged on the area.
The shooting comes two days after an Islamic convert ran down two Canadian soldiers with his car, killing one, near Montreal, before being shot and killed by police.
There were various accounts of the incident, with one saying there were "numerous gunmen" at the Canada War Memorial on Monday's shooting. Authorities are working to figure out if there were two or three gunmen, one sources was quoted as saying.
When the shooting ended, a person was lying motionless on the ground near the library entrance, said another source.
A "lone gunman is deceased" after shots were fired in Ottawa, Canada, a member of the nation's Parliament, Bob Zimmer, tweeted.
However, there were reports later that there may have been further shots fired at Canada's Parliament.