The feature, which is only switched on in times of emergency, allows users in the area of the crash to let Facebook friends and family know they are safe. It also allows people in the area to offer volunteer services, such as food, transportation or shelter.
Users can also send messages to loved ones through the page asking them if they are safe.
The check-in has also been activated during other emergencies, like the 2017 terror attack in Barcelona, that left 13 people dead and 50 injured after a white van deliberately plowed through a crowd.
Toronto police are still investigating the driver who plowed his white Ryder rental van in the Yonge Street and Finch Avenue area of North York around 1:30 p.m. ET.
One suspect has been taken into custody.
At least one witness described the driver as appearing to deliberately target victims during his roughly 1.6-km-long rampage.