Ontario's police watchdog is investigating after a man was shot by police in Nepean Saturday night.

In a media release Sunday afternoon, the Special Investigations Unit (SIU) said a 28-year-old man was taken to hospital with serious injuries after an exchange of gunfire between him and police officers.

The SIU said Ottawa police got a call around 9:40 p.m. Saturday from someone who told them they were concerned about the man and that he had firearms.

When officers arrived at the townhouses on Garden Glen Private, they tried unsuccessfully to contact the man by calling him on the phone and knocking on the door, the SIU said.

"Some time later, there was an exchange of gunfire between the man and police," the SIU said in the release.

Witness describes 'shocking' scene

Neighbour Claudia Goupil said she watched the altercation unfold from her townhouse's top window. She said she could hear and see rifle-carrying SWAT team members approach the front door of the man who was shot.

"They were trying to get him to come out with his hands up," Goupil said.

"I don't know what came first, honestly. [The gunshots] came fast, came loud. But I did hear the cop saying [the man] had a pistol in his right hand just before they fired."

3 officers fired guns

Three officers fired their guns and the man was struck, the SIU said. He then retreated into the home and eventually surrendered.

Goupil said the man re-emerged from the house about 20 minutes after the gunfire.

"He was wearing just boxers, and he came out with his hands up and seemed a little bit injured," she said, adding that she knew him from the neighbourhood but not personally.

Video footage taken by Goupil after the gunfire, which she shared with CBC, shows the man obeying officers' commands to lay down on the ground and keep his arms at his side.

Warning: this video contains images some may find distressing. 

The officers are later heard ordering anyone else who may be in the house to come out.

"Nothing happens in this neighborhood. So it was a little bit shocking, actually," Goupil said.

The SIU has assigned three investigators and two forensic investigators to the case. It's also looking for any information related to the incident, including any photos or videos.

The unit investigates cases of serious injury, death and allegations of sexual assault involving police, as well cases where police discharge firearms at people.

The Ottawa Paramedic Service said it was at the scene but had no further comment, citing the SIU investigation. The SIU said Sunday evening that the man was in hospital in stable condition.

In a statement, Ottawa Police Association president Matthew Cox said they were thankful none of their officers were hurt and that "incidents like this demonstrate the dangers our officers can face when responding to calls for service."

CBC has also reached out to the Ottawa Police Service for comment but had not heard back by early Sunday evening.