Ottawa police were called to a home near the intersection of Albion Road and Cahill Drive, close to the South Keys Shopping Centre, at around 7:20 p.m local time.
As of 9:30 p.m., about 20 officers remained on the scene, including a police negotiator, CBC News reported.
Police said roughly one hour later that a suspect was still barricaded inside the home on Cahill Drive.
They urged people living nearby to stay inside and follow officers' instructions.
According to police and Ottawa paramedics, a male of unknown age was shot and pronounced dead at the scene.
A young woman was also shot, paramedics said. She was rushed to the Ottawa Hospital's trauma centre in critical condition.
Neighbors told CBC News that there had been a loud argument taking place at a barbecue prior to the shooting.
Police said they have also been evacuating some nearby residents from their homes.
As of 9:30 p.m., no suspects had been arrested.