A 15-year-old boy who was shot by police outside a Pizza Pizza in Mississauga last month has died, the province's police watchdog says.

The shooting took place just before 2 a.m. on July 27, after Peel Regional Police responded to a call for a robbery involving three young men at a gas station in the area of Creditview and Britannia roads.

According to the Special Investigations Unit's preliminary investigation, two of them fled before police arrived. Another allegedly went on to try to rob a different establishment, and also unsuccessfully attempted to break-and-enter into three different vehicles.

When officers arrived at the scene, the SIU says, they located the 15-year-old outside a bank in the plaza.

"There was an interaction and one police officer discharged a firearm," the SIU said in July, when it took over the investigation. At the time, it said the teen, who was rushed to SickKids hospital, was in serious but stable condition.

The SIU, an arm's-length agency that probes incidents involving police that result in serious injury, death or involve allegations of sexual assault, said six investigators and two forensic investigators were assigned to the case.

The agency said it isn't releasing the name of the teen who died.

In July, a woman who alleged the teen entered her car, told CBC Toronto that she was the person who called 911 and that she provided video footage of herself speaking on the phone that included the moment the boy was shot by an officer.

CBC Toronto also obtained video taken shortly before police wounded the teen, showing him speaking to a Pizza Pizza employee before pulling a gun from his sweatshirt pocket and holding it roughly 10 centimetres from the employee's face. The video then shows the employee grabbing for the muzzle of the gun, attempting to wrestle it away from the teen.

Multiple employees at the Pizza Pizza told CBC Toronto they believed the business was targeted.