Mark Vijay Chahal was born in 1966 in Canada and worked as an accountant. He married Rajwar Kaur Gakhal in 1994, but their marriage was short-lived due to allegations of domestic abuse. Rajwar filed complaints against Chahal with police in both Burnaby and Vernon, British Columbia. Despite these complaints, Chahal had no criminal record, and his firearms were legally registered. The couple separated in January 1995, and Rajwar returned to live with her family in Vernon.

On April 5, 1996, Chahal drove from Burnaby to Vernon, British Columbia, in a rented van, leaving his personal vehicle at Kelowna Airport. He checked into the Globe Motel under the alias "Singh" and paid in cash. At approximately 10:30 a.m., he arrived at the Gakhal family home on Okanagan Avenue, where preparations were underway for the wedding of Rajwar's sister, Balwinder.

Chahal approached the house armed with a .40-calibre Smith & Wesson semi-automatic pistol and a .38-calibre Smith & Wesson revolver. He first shot his father-in-law, Karnail Gakhal, who was washing a car in the driveway. He then entered the home and proceeded to shoot eight more individuals: his estranged wife Rajwar, her mother Darshan, her brother Jaspal, sisters Balwinder, Kalwinder, Harvinder, and Jasbir, and brother-in-law Roger Saran. Two others, including a six-year-old girl, were injured but survived. Two young children were left unharmed.

After the massacre, Chahal returned to his motel room, where he wrote a note apologizing for his actions and listing contact numbers for his relatives. He then shot himself in the head. A 12-gauge pump-action shotgun was found in his vehicle but was not used in the attack.

The Vernon massacre was, at the time, the deadliest mass shooting in Canada since the 1989 École Polytechnique massacre. It remains one of the most devastating instances of domestic violence in Canadian history. The tragedy prompted discussions on domestic abuse, gun control, and the importance of supporting victims of domestic violence.