Police say they were contacted at 12:31 p.m. Thursday regarding a shooting incident on White Oaks Court, near Dundas Street and Cochrane Street.
Officers responded and found four male victims, who are now receiving medical attention in hospital. Three of the victims are in serious condition, and one is in critical condition, according to Durham Regional Police.
Durham emergency workers said that four people were taken to Rouge Valley hospital.
One victim, a 19-year-old male, was transported from the local hospital by air ambulance to Toronto's St. Michael's Hospital with serious injuries at about 1:30 p.m., according to Ornge air ambulance service.
The other three suffered injuries that aren't considered life-threatening, said Sgt. Nancy Van Rooy of Durham Regional Police.
No suspects found, police say
"We responded with a number of units to the scene, and we were not able to locate the suspect or suspects involved in the shooting," said Sgt. Van Rooy.
"We continue to canvas the area looking for any co-operation from the public, and witnesses that can help further the investigation."
No arrests have been made, she added.
Police would not confirm where in the building the shooting took place, or whether guns or other evidence have been seized because it was still early in the investigation.
"We have a lot of information that we feel is necessary to withhold," said Sgt. Van Rooy.
The identities and ages of the victims have not yet been confirmed, she added.
Homicide investigators and the police canine unit are on the scene, she said, and there may be surveillance video to be reviewed, Sgt. Van Rooy added.
Police cordoned off the scene of the shooting, as officers searched the area for suspects and spoke to witnesses.
Apartment residents heard gunshots
Dana Saleh, a nurse who lives in an 18th floor apartment in the same building, said she was in her living room on Thursday afternoon when she suddenly heard sirens.
"I step out on my balcony, and I see basically the entire street and the entire court, basically, just flooded with police cars, cruisers, EMS ambulances," she told CBC News, adding that she saw at least three people taken out of the building on stretchers by emergency workers.
Jillian Vice was with her husband in a building across the street when they both heard a noise at about 12:30 p.m.
“I wasn’t quite sure if it was a bang or what it was,” she told CBC News in an interview.
Within a few minutes, she heard sirens approaching. When police flooded the scene, Vice said she wanted to know what was going on.
After hearing media reports that four people had been shot, Vice got out her camera and recorded what was happening.
Vice also saw three victims taken out of the building on stretchers.
Another witness who lives in the building where the shooting took place said she heard an "extremely loud, loud noise."
"In my mind, I thought the elevator was falling from the penthouse level all the way to the ground. I never heard a gunshot before," the witness, who didn't want to be identified, told CBC News.
She was on her way to the building laundry room and when another resident told her it was gunshots, she said she was surprised.
"Doesn't make me feel too easy and everything," she said. "Like, sometimes you don't know who the neighbours are because of the size of the buildings."
Another woman said she wants to leave the area.
"I'm really very scared. We [are] all thinking move out because we are here, like a year, and this is, like, the third time something like that has happened," said one woman who spoke to CBC News.
But Vice said she feels the neighbourhood is safe.
"Wherever this happens — something like this — it always gets major media attention and then everyone thinks 'Oh, that's a bad area, No one would ever want to live there. But, like, the majority of the people are nice and they're decent people. And something like this is going to get media attention no matter where it is," said Vice.
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