"He just stayed on the ground mumbling," Canyon told the Idaho State Journal. "I thought he was playing with his toy, but I saw the toy a couple yards away from him ... So, I called him again and got really scared."
Canyon rushed toward him and held him, seeing something was terribly wrong. "[I] saw this red froth coming from his mouth and his eyes turning glassy," he said.
He ran down the hill for help and, when he and his parents returned a few minutes later, Casey was dead.
Later the family would discover that their 3-year-old dog had been poisoned by an M44, a cyanide trap that is set out by the U.S. government to kill coyotes, luring them through scented bait.
"M44s are incredibly dangerous by nature of what they are," Brooks Fahy, executive director of Predator Defense, a nonprofit based in Eugene, Oregon, told The Dodo. "They put a scent lurer - like urine from a coyote in her heat cycle or another smell that makes the animal want to grasp the M44 head - and any coyotes, wolves, are attracted to it. They pull on it and that's when it goes off."