Our friend had a horse the went down in the middle of the night ( she was at a newer barn - a few months at most) . It was 40 below - she is older and was in an unheated metal only barn. The vet came and gave it something (not sure yet) and within 2 secs it had a seizure - dropped to the ground eyes back, thrashing etc.
I guess it stopped and they got it up. All left for a while as the horse seemed OK ( not sure what happened next) but the horse died in the next few hours. This vet is not a large animal. Any idea of what caused the seizure - injection site wrong?