The pregnant mare who was shot as she was about to foal.
Doreen Henderson, of the Wild Horses of Alberta Society, wrote on its website that she wept at the sight of the dead horses when she got there close to dark.
"I walked to each dead animal and studied it and wept at their senseless, violent deaths. Each horse still somewhat warm to the touch, I gently touched their faces and said a prayer for them," she wrote.
Henderson said the victims were a mare heavy in foal, a yearling colt and a 2 to 4-year-old stallion.
They all had bullet wounds.
Henderson reported that the first person on the scene found the stallion was still alive. "He left to get a gun to put it out of its misery, but when he returned the stallion was dead as well."
The mare had her birthing sack hanging out of her and on closer inspection you could see the tiny hooves sticking out, she said. The yearling colt had taken a bullet to the chest and had ran uphill about 80 metres before collapsing.
There are unconfirmed reports that a reward offered for information leading to the conviction of those responsible has reached $C20,000.
The three wild horses are not the first to be shot in the Sundre area, about 100km northwest of Calgary.
Nearly two dozen horses have been found shot in the area since 2004.
The maximum penalty for anyone convicted of killing the horses is five years imprisonment.
There are about 300 wild horses in the Sundre area, originating from domestic horses used for logging and mining in the early 1900s.