Claudia Huber and her husband Matthias Liniger were attacked at their home in Johnson's Crossing.
Mr Liniger fired several rounds at the bear as it was mauling Ms Huber.
The bear was shot and died, but one bullet ricocheted off a tree and killed Ms Huber, according to Kirsten Macdonald, Yukon's chief coroner.
"What transpired at that property on that day was an absolute, catastrophic collision of events," Ms Macdonald said, according to CBC.
Mr Liniger said: "It was almost already too much what happened there, what I saw, what I heard."
"And now I have to somehow get over that fact, too, that a bullet killed her," he went on.
The coroner's report noted that Ms Huber tried to play dead during the attack, which is not the recommended course of action in this situation.
Ms Macdonald said the best response during a predatory bear attack is to fight back.
The report called for better public education on what to do in different kinds of bear attacks.
A woman mauled by a bear at her home in Canada's Yukon Territory was killed by a bullet fired by her husband while trying to rescue her, a coroner says.