The Special Investigations Unit has invoked its mandate after two people were killed in a police involved shooting in the ByWard Market overnight Friday.

The SIU says that shortly around 2 o'clock an Ottawa Police officer driving in the area of Dalhousie Street and Clarence Street heard a gun go off and proceeded to exit his vehicle. The SIU says there were three different scenes involved in this one fatal event.

"A man was shot on the west side of Dalhousie Street just North of Clarence Street," says Jason Gennaro, the SIU's spokesperson. "The officer tried to arrest a male suspect in relation to the shooting."

Gennaro says that suspect fled the scene and the officer pursued him on foot. The male suspect then shot and killed a 43-year-old man on Dalhousie Street.

"The police officer then followed the male suspect inside a parking garage on Murray Street, East of Dalhousie Street," Gennaro says. "There was a confrontation between the police officer and the man who had fled. Several shots were fired and the man was pronounced dead at the scene."

The 31-year-old suspect was pronounced dead at the scene. The officer involved in the confrontation was not injured.

The SIU says it is too early at this point in the investigation to determine or talk about what led to the initial confrontation or the escalation of violence.

Seven investigators and three forensic investigators with the SIU have been deployed to lead the investigation. The SIU is called in to investigate any incident involving any police service in Ontario where there is serious injury, report of a sexual assault or death. Ottawa Police is also investigating.

"The unit is asking anyone who may have witnessed the incident to contact our lead investigator," Gennaro says. "We are also asking anyone who may have video evidence of this incident to upload that to the unit website."

The names of the vicitms have yet to be released. How or whether the victims and suspect are related is unclear.

No charges have been laid.

More to come.