For the past three months, Gjermund Roesholt and his family lived far off the grid in the Yukon, the vast, desolate Canadian territory where wildlife outnumbers humans. They traded life in the city for a cabin on Einarson Lake, a remote speck of water amid snow-capped mountains, and spent their waking hours fur trapping.

On Monday afternoon, Mr. Roesholt had almost finished the return trek from his trapline to the family’s cabin when a grizzly bear appeared and charged him, the authorities said. He pulled out a gun and killed the bear, but soon discovered a gruesome sight: Outside the cabin were the bodies of his wife, Valerie Theoret, 37, and their daughter, Adele Roesholt, who was 10 months old.

They had been mauled to death by a bear, most likely the same one Mr. Roesholt shot, the Canadian authorities said.

In the Yukon, it is common for people and bears to interact, both in the wild and in towns, where the animals sometimes venture and rummage through trash for food. But it is not normal for the interactions to turn violent, let alone fatal. In the past 20 years, only three people in the territory have been killed by bears, according to the Yukon Department of Environment.