Fourteen-year-old Canyon Mansfield was walking his dog on farmland near his Pocatello, Idaho, home last week when he saw what he thought was an old fire-sprinkler head sticking up from the ground.
He tapped it and the spring-loaded device launched a powdery cloud, leaving his face and hair coated with an orange substance. He used snow to quickly wipe most of it away. Then he saw Casey, his 3-year-old yellow Labrador, motionless on the ground.
Mansfield tried to wake up his dog. But within minutes, Casey was dead.
The culprit was an M-44, a device filled with a cyanide compound that is routinely used near farms and rangeland by the U.S. Department of Agriculture to kill coyotes and other livestock predators. Critics call it a "cyanide bomb."
The device, invented in the 1960s and later deployed across the West, consists of a hollow metal tube 5 to 7 inches long loaded with 0.9 grams of sodium cyanide powder and coated with odorous bait. When an animal bites down on the chamber, the powder flies into its mouth, contacts saliva and forms deadly hydrogen cyanide gas. The animal is rendered unconscious almost immediately and dies within five minutes.
Last year 12,511 coyotes were intentionally killed that way, along with 688 foxes and 10 feral dogs, according to the Agriculture Department, which defends the device as useful and necessary.
But the government also reported the unintentional deaths of 180 foxes, 57 raccoons, 30 opossums, 22 feral dogs, 21 skunks, three birds and a black bear — as well as seven domestic pets or livestock.
Predator Defense, an activist group in Eugene, Ore., that has been pushing for legislation to ban the devices, says it believes that tally of unintentional deaths is incomplete because many are not reported.
The Sacramento Bee reported in 2012 that U.S. records show more than 3,400 animals were mistakenly killed by M-44s between 2006 and 2012.
Wildlife Services said in a statement to reporters that the latest incident was the first "unintentional lethal take of a dog" by an M-44 in Idaho since 2014. Two other dogs died in Wyoming from the devices this month, and a wolf was unintentionally killed by a device in Oregon in February.
"Wildlife Services understands the close bonds between people and their pets and sincerely regrets such losses," the statement said.
R. Andre Bell, a spokesman for Wildlife Services, said that "the government posts signs and issues other warnings to alert pet owners when wildlife traps or other devices are being used in an area for wildlife damage management."
Still, Bannock County Sheriff Lorin Nielsen said the cyanide bomb was news to him. "I've been a sheriff here for 20 years and worked for the office for 39 years," he told Idaho reporters, "and I've never heard of leaving around a device that emits poisonous gas."
The Mansfield family said there were no warning signs where the Labrador was a killed, a plateau about a quarter-mile from their home. The remaining M-44s in the area have since been removed, according to Wildlife Services.
There are no reported human deaths as a result of the cyanide devices, though people have been treated for nausea, vision impairment and other symptoms.
As for Mansfield, he is being monitored for any effects of having ingested the toxic compound. He told authorities that he had no idea why the device was there or what its purpose was.
"This is horrific," his mother, Theresa Mansfield, told the Idaho State Journal. "This is like terrorism in my backyard."