A 21-year-old B.C. woman is fighting for her life after she and her twin sister were attacked Wednesday by a Rottweiler-cross dog.

The critically injured woman was bitten more than 100 times and left with a fractured arm and detached bicep, according to Richmond RCMP.

Her twin was seriously hurt too, but a three-year-old boy was left uninjured.

RCMP said the dog belongs to the boyfriend of one of the women.

Retired letter carrier Ken Brodie, 73, witnessed the attack and was also bitten while attempting to pull the dog from one of the victims.

Brodie said her heard screaming, so he hopped his backyard fence, where he saw one of the women lying on the ground.

“The dog kept coming at her. Ripping, ripping, ripping.”

Brodie said he kicked the dog, “giving him a pretty good boot,” and tried to haul it off, “but of course I got bit myself.”

“It was bleeding so bad I couldn't stay,” he added.

A police officer arrived and shot the dog, which survived and was sent to a city shelter, where authorities will decide whether to euthanize it.

The attack was the second severe dog attack in B.C. in a week. On Christmas Day, two pit bulls entered a home in Fort St. John, B.C., killed a cat and attacked two people -- one of them so badly that he may lose an arm.

With a report from CTV Vancouver’s Jon Woodward