You can read about it CTV Calgary- A dozen horses die in an accident on Deerfoot - CTV News, Shows and Sports -- Canadian Television
I saw the accident (or rather when they were trying to unload the horses). I believe it happened at about 6:30am ish, because by 7:30am, when I was driving through, they were trying to break open the trailer with a saw and unload some of the horses, and the loose horses had been coralled.
It was horrific
The only good news is that the responders were quite quick in getting there, I'm told. They had more then 3 vets on site. And Spruce was right around the corner and brought their horse ambulance and extra rope and wire so they managed to corral the loose horses before anything worse happened, as that road can get quite busy.
Especially since I later found out that they were Fort Macleod bound