A 14-year-old boy was hospitalized and his dog killed when he picked up a government-planted, cyanide-filled 'bomb' near his Idaho home, causing it to spray them both with the toxic substance.

Canyon Mansfield, 14, was playing with his yellow Labrador retriever, Casey, near their home east of Pocatello Thursday afternoon when he bent to pick up what he thought was a sprinkler head on the ground, causing it to go off.

'Canyon said there was a bang like a bomb,' said mom Theresa Mansfield, 'then an explosion of an orange substance that covered him and Casey, who was writhing in pain on the ground before he died right in front of Canyon.'

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Tragic: Casey (left), a three-year-old Labrador, was killed by an M-44 cyanide bomb (right, stock photo) on Thursday in Idaho when it was picked up by his owner Canyon Mansfield, 14

Toxic: Canyon (pictured) must now have his toxicity levels checked daily. His family and first responders also had to undergo decontamination. The trap was placed for coyotes

Video courtesy of East Idaho News:

The boy - who was sprayed in the face, and continues to undergo toxicity tests - says he didn't realize at first what was happening to his best friend.

'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.

'I sprinted toward him and landed on my knees and saw this red froth coming from his mouth and his eyes turning glassy and he was having a seizure.'

The boy's father, Pocatello physician Mark Mansfield, rushed to the scene and pounded on the 90-pound dog's chest in a futile effort to revive the animal.

Both the family and first-responders underwent decontamination procedures, and Canyon was tested for cyanide poisoning at a hospital for the second time Friday, officials and family members said.

He must now undergo daily check-ups to monitor his toxicity levels.

It later emerged that the M-44 bomb had been placed near the home by Wildlife Services, an arm of the US Department of Agriculture (USDA), which is targeting coyotes in the area.

M-44s are loaded with 0.9 grams of sodium cyanide and covered in smelly bait, in the hope of attracting animals.

When something triggers the 5-7-inch tubes, a spring-loaded trap sprays the cyanide into the face of whatever is nearby.

Furious: Madison, Canyon's sister, said she was furious with Wildlife Services, which placed the bomb. Canyon said that he didn't see warning signs, which are required by law near bombs

Under USDA guidelines, signs must be placed around the location of the traps in both English and Spanish to avoid accidents from occurring.

But Canyon said he didn't see any signs and that 'I would have noticed it because I go up there all the time.'

Bannock County Sheriff Lorin Nielsen also said that there were no obvious warning signs, although the case is still under investigation.

The agency has been sued by conservation groups claiming that its programs to poison, trap and shoot various predator species violate federal environmental and wildlife protection laws.

Thursday's incident marked the first 'unintentional lethal take of a dog' by an M-44 in Idaho since 2014, and Wildlife Services seeks to minimize hazards to pets and humans by posting warnings, spokesman Andre Bell said.

'These devices are only set at the request of and with permission from property owners or managers,' the agency said. They are 'spring-activated' and 'not explosive devices,' it said.

Posting on Facebook, Canyon's sister Madison took issue with the department's claims.

Agony: Canyon (far right) said he watched Casey write in agony, red foam spilling from his mouth, before the pup's eyes went 'glassy'

'The USDA's statement regarding the horrific incident that happened to my family yesterday is both disrespectful and inaccurate,' she wrote.

'The USDA intentionally refers to the brutal killing of our dog as a "take" to render his death trivial and insignificant. They also claim that the killing of an unintended victim is a rare occurrence, but this is entirely untrue.

'In fact, this issue is nationally recognized due to the lack of selectivity of cyanide bombs, and there have been many reported incidents in which unintended animals and people have been targeted.'

According to USDA statistics hosted on the anti-trapping website Predator Defense, between 2003 and 2014, 930 dogs were killed by M-44s. In that same period they killed 150,881 coyotes.

However, Predator Defense says the statistics are 'highly suspect' as 'employees within Wildlife Services have repeatedly told us many deaths are not reported.'

The organization says its mission 'is to protect native predators and end America's war on wildlife.'

Sheriff Nielsen, who described the devices as 'cyanide bombs,' also said no notice was given to authorities about their placement.

'I've been a sheriff here for 20 years and worked for the office for 39 years, and I've never heard of leaving around a device that emits poisonous gas,' he said.

Nielsen said he intended to meet federal officials next week to 'get to the bottom of this.'

He added: 'The trapper that set those for the federal government did show up, we were able to interview him and he has disarmed those that are in that area, and hopefully the rest of the county.'

Theresa Mansfield said Wildlife Services had not sought to contact the family to apologize for the incident.