The seven-year-old from Ajax, Ont., was riding in a Honda Odyssey minivan along with his parents and five other children when the vehicle was struck from behind by a Hummer on Highway 401.
Toronto police Const. Blair McDonnell was driving along the same stretch of highway with his own family when the crash happened in front of them.
"It could have been us. We were seconds behind it happening," McDonnell said during an interview Sunday afternoon.
When attending a fundraiser for Jacoub in Bolton, Ont., McDonnell told CBC News about the moments after the crash, when he was one of the first people on the scene.
His wife, a police officer herself, tried to keep Jacoub's mother calm, while McDonnell and an off-duty firefighter attended to Jacoub.
"When I got there, there was a firefighter in the back seat performing CPR on little Jacob and I climbed in through the trunk to help [do] what I could to revive the boy and give him his best chances before ambulance and fire got there," McDonnell said.
Jacoub was rushed to hospital after the crash, but succumbed to his injuries.
The Hummer fled the scene and was later found abandoned.
In the days that followed the deadly crash, the Favila family appealed for the driver to come forward and police searched for the suspect.
On Friday, police announced that an arrest had been made in Cobourg, Ont., about an hour east of Toronto.
A 30-year-old Toronto man has since been charged with dangerous driving, criminal negligence causing death and failing to remain at the scene of an accident.