Chiefs say the slaughter of the migrating herd is a huge waste, especially in the eyes of native hunters who use every part of the animal down to the tongue and the blood.
"The caribou were pretty much slaughtered," said Grand Chief David Harper, who represents northern First Nations. "They took their antlers and basically left the meat. That kind of action is totally uncalled for ... You don't even call that hunting if you are just taking away the antlers.
"We're very disgusted."
Barren ground caribou aren't considered at-risk, but native leaders say their numbers are declining. While aboriginals still hunt the animals for food and clothing, chiefs say the province should be cracking down on wasteful, recreational slaughter.
Along with the investigation, they're also calling for more patrols by conservation officers on winter roads.
Provincial officials didn't immediately respond to requests for comment. Aboriginal chiefs say they were told by conservation workers in Thompson that the slaughter could have been carried out by about 15 licensed hunters who were each legally allowed to kill two caribou.
Chief Joe Antsanen with the Northlands Denesuline First Nation came across the gruesome discovery near Lynn Lake while travelling to Winnipeg for a conference last week. The bloody scene was "heartbreaking," he said.
He also said it couldn't have been perpetrated by First Nations hunters.
"We have respect for caribou. We take all the meat, even the hide, we make good use out of that," Antsanen said. "A terrible, terrible slaughter took place ... It's something that I can't let go."
It's not the first time Antsanen has encountered such a thing. Last year he came across severed caribou heads that had been spray-painted various colours by the side of the winter road.
Antsanen hasn't contacted provincial authorities directly about his latest find. He said he wanted to go to the media first with graphic photos he took to show the seriousness of the slaughter.
The images disturbed Jack Robinson, an elder who has been hunting near Thompson for years. He said he's also come across caribou that have been shot for no apparent reason other than recreation — but never on this scale.
"It bothers me to see the slaughter," he said. "This is just terrible. We take everything from the animal — the tongue, the kidneys, the heart. We don't waste anything. This has to stop."
The chiefs say they have posted a reward for any information that helps track down the perpetrators. They are also planning a ceremony to honour the dead caribou.
Chief Jimmy Thorassie with the Sayisi Dene Nation said the waste of such prime meat is particularly disgusting given the high cost of food in remote northern communities.
"The cost of food is outrageous," he said. "Why would we want to do something like this?
"To see this is very sad."