Three adults are dead and two children and a man were sent to hospital with injuries after a crash just south of Three Hills, Alta., Friday night.
A collision analyst is on scene trying to piece together what happened when two pickup trucks collided.
One truck was hauling a horse trailer when it happened. The collision left one horse dead and another injured.
Both vehicles burned after catching fire.
"It's one of the most horrific collisions I've seen in my career," said Sgt. Patricia Neely.
Speed and alchohol are not believed to be factors, but RCMP are considering mechanical failure as a possible cause.
RCMP temporarily closed Highway 21 at Township Road 310 to traffic.