The bear lunged at the woman and bit her, breaking her arm in a "chance encounter" on Friday, said Len Butler of B.C.'s Conservation Officer Service.
The bear was just trying to protect itself as it happened upon the woman and her boyfriend, he added.
"They hiked along a trail, they were in some of the open meadows and there was a small little pass to go up through," said Butler.
"It was so quick. They did nothing wrong."
The incident occurred about mid-afternoon while the pair from Williams Lake, B.C., was ascending in the Big Slide Mountain Area near the community of Horsefly, in the province's Cariboo region.
It was a blustery day, meaning winds were diffusing the hikers' scents and obstructing the crunch of their boots along the foliage, said Butler.
The couple emerged upon a knoll about the same time the animal arrived from the opposite direction uphill.
The bear and hikers were only about seven to nine metres apart when they spotted each other.
"They kind of starred at each other for a second, then the bear bluff-charged and stopped," Butler said. "Then the bear lunged at the female, grabbed her arm, threw her to the side and the bear then just immediately ran off into the trees."
Butler described the bear's reaction as standard and said it took the path of least resistance to escape.
He said the woman, in her mid-20s, had bear spray holstered to her hip but simply couldn't respond fast enough.
"It's more of a surprise — shock value probably for both."
The pair hiked about an hour back down the mountain before driving two more hours to Royal Inland Hospital in Kamloops, B.C., where the woman was treated.
B.C. Interior Health released a statement on behalf of the couple.
"As you can imagine, the experience was startling, terrifying and one that caused physical injury," said the statement issued by the woman named River and her boyfriend Evan, who declined to publicize their last names.
"Being outdoor enthusiasts, we both accept the risks of exploring beautiful British Columbia and we don't want this very rare experience to deter anyone from enjoying the great outdoors.
"Just ensure you are prepared in case of any unexpected emergency, as we know this saved our lives."
Conservation officers retraced the couple's path to the location of the attack. They closed the file and noted no sign of the bear remained in the area, said Butler.
Surprise bear attacks are fairly common across the B.C. backcountry, he said, and bears may be out in higher numbers because there is fresh vegetation for feeding and mating season is just ending.
— Written by Tamsyn Burgmann in Vancouver
Follow @TamsynBurgmann on Twitter
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