The grizzly bear that killed a Canadian schoolteacher and her infant daughter was injured and desperate for food, according to a government investigation which concluded the tragic attack could not have been prevented.

Valérie Théorêt, 37 and Adèle, 10 months, were killed in November by a male grizzly bear in an unprovoked attack as they walked close to the family’s remote cabin in the Yukon.

The territory’s chief conservation officer, Gordon Hitchcock, told reporters on Wednesday that the 18-year-old bear was severely emaciated, weighing only 137kg (302lb) and lacked critical fat stores needed for hibernation.

“This bear had started turning to uncommon food sources and was in pain from having previously consumed a porcupine to avoid starving to death,” said Hitchcock. “Bears do not typically eat porcupines.”

An examination found spines from the porcupine had pierced the bear’s stomach, likely causing it intense pain and preventing it from hunting as winter drew nearer.

Officials believe the bear saw and followed snowmobile tracks left by Théorêt’s husband, Gjermund Roesholt, who was away checking fur traps. The bear is thought to have arrived at the family cabin near Einarson Lake, a remote area 400km (250 miles) from the territory’s capital of Whitehorse. The bear probably spotted Théorêt and her daughter, hiding among brush until it could strike.

“The attack appeared sudden. All evidence suggests Valérie did not have time to react,” said Hitchcock.

When Roesholt returned to the cabin, the bear charged at him. He shot the bear four times, killing it. Soon after, he found his wife and daughter.

A postmortem on the pair revealed that the two died almost instantly from the attack.

“This was a very difficult case, I think, for all of us involved,” Yukon’s chief coroner, Heather Jones, told reporters.

Officials lauded the family’s adherence to safe practices in the backcountry, meant to deter wildlife encounters; they kept food sources from the cabin and stored bait for their fur traps on the other side of the lake.

Officials emphasized that bear attacks remain incredibly rare.

“To say that the victims were in the wrong place at the wrong time sounds trite, but our investigation shows that more than anything else, this was an unfortunate tragedy and that little could have been done to prevent it,” Hitchcock said.