CALGARY — Family of a Calgary wife and mother who died when a rock smashed through the windshield of her family car in southeastern BC have gathered here — devastated by the tragic and random loss of a loved one.

Janice Cairns was a passenger in the Subaru Legacy travelling northbound with her husband and their two sons on Hwy. 93/95 near Canal Flats, BC, on Friday when a large piece of rock became dislodged from a southbound semi with an unloaded low-bed trailer, police said.

She and her family — husband Nigel, three-year-old Liam and eight-month-old Ryan — were celebrating Thanksgiving weekend in nearby Kimberley, BC, and had taken a day trip out to Fairmont Hot Springs.

"We're all grieving," Janice Cairns' brother, Richard Lam, said.

"It's a huge hole in all of our lives."

The rock that hit Cairns was about 30 cm by 13 cm. Coroner spokeswoman Barb McLintock said Cairns was killed "virtually instantaneously."

"My feeling is this was just one of those things," McLintock said.

"There are very few crashes and collisions that we think are completely unpreventable...maybe there is something that we don't know about yet."

After the impact, Nigel Cairns drove looking for the nearest hospital, which would have been 50 km north, in Invermere, BC.

He stopped about halfway, near Fairmont, where police, fire and paramedics came to him.

Cairns, who recently celebrated her eighth wedding anniversary, is originally from Vancouver.

Lam explained his sister chose raising a family over a career as an information technology professional, and that's how she'll be remembered — devoted.

"She loved her family, very much," Lam said.

"She always wanted to be with her boys — they did everything together."

Police later found and seized the semi in Wasa, BC, about 47 km south of where the rock smashed Cairns' car. The driver was taken into custody but was later released without charges.

"I don't think the truck (driver) would have known that something had happened behind him," Staff Sgt. Marko Shehovac of the Columbia Valley RCMP told QMI Agency.

Nobody else in the car was injured.