The province's Special Investigations Unit is investigating a shooting that happened in Thornhill, north of Toronto, on Monday night. (Tony Smyth/CBC News)

The province's police watchdog is investigating after two people died in a violent attack north of Toronto on Monday night.

York Regional Police were called to a residence at 11 p.m. on Cottonwood Court, which is near John and Bayview streets in Thornhill.

Police say upon arriving, officers found a 47-year-old woman “with injuries consistent with stab wounds.” Officers approached a 50-year-old man at the scene. An altercation ensued and the man was shot by police. Both the man and the woman died of their injuries.

There are unconfirmed reports that the couple are husband and wife.

Claire Sun, who lives a few doors down from the crime scene, was trying to fall sleep late Monday when she was startled by the sound of gunshots. Sun said she recalled a domestic incident at the same house last year.

"The woman was hurt last time as well," she said.

A neighbour who did not want her name used said her daughter was best friends with a 17-year-old girl who lived at the home, adding that the residents had a history of domestic problems.

Ontario’s Special Investigations Unit (SIU) is investigating.

The SIU investigates incidents involving police officers in which civilians are killed, seriously injured or may have been sexually assaulted.

Neighbours said they saw a teenager believed to be the woman's daughter outside screaming.

"We just heard a woman crying out, 'He's dead, he's dead'," recalled Hoorish Hayderi.

Residents in the area told CBC News reporter Lucy Lopez they were shocked to learn that a shooting had occurred in their neighbourhood.

“People who’ve lived here for 25 years say nothing like this has ever happened,” Lopez reported on Tuesday morning.