Article is in French from a local newspaper... There are 3 videos attached to the story.
The flight had just taken off from Montreal for Shanghai when they had to shutdown an engine. It was decided to dump fuel before landing back in Montreal.
Unknown if the shutdown was right after takeoff or sometime after. But there is talk that they went north of Montreal and possibly dumped fuel for 30 minutes prior to returning for the landing.
Atterrissage d'urgence à Montréal, aucun blessé | Louis-Samuel Perron, Audrey Ruel-Manseau | Faits divers