York Regional Police are upgrading the charges against a 16-year-old driver who allegedly hit three people with his car on Sunday, May 16, in Vaughan.

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A 4-year-old boy and his 10-year-old sister were struck by the car and taken to the hospital with life-threatening injuries, but have since died, police say. They say an adult male was also taken to the hospital for non-life-threatening injuries.

680 News reports that the children were outside of their home on Athabasca Drive with a neighbour who was helping them with a bicycle chain when the black Mercedes lost control and struck them in the driveway.

The driver was arrested at the scene and now faces a total of six charges, including two counts of criminal negligence causing death.

Police are asking for any witnesses who may have any information or dashcam footage of the incident to come forward or submit photos and videos through a digital evidence portal that has been opened for the investigation.

Vaughan's mayor calls the tragedy a "senseless act"

City of Vaughan Mayor Maurizio Bevilacqua reacted to the news on Twitter on Monday.

"Losing a child is a pain no parent should ever have to experience," he wrote. "Learning the 10-year-old girl struck during Sunday's reckless driving incident has passed away is devastating news.

"Sending prayers & strength to the family. Two lives were taken too soon due to this senseless act."

A neighbour named Elizabeth Lincoln described the 4-year-old boy as a "delightful child" and a "sweetheart" to CP24. A memorial has been set up outside of the siblings' home, where members of the community have laid flowers and stuffed toys.