The bear, which weighed at least 190kg, was later killed when it charged wildlife workers who were investigating the attack.
Charles Mock, a 40-year-old Montana backcountry guide, was killed by a male grizzle bear just outside Yellowstone national park on Saturday, local authorities said.
It’s thought the bear attacked Mock because it was defending a nearby moose carcass.
According to Christine Koosman, a Gallatin county sheriff’s office spokesperson, the guide was fishing alone in the forest along the Madison River, a few miles north of West Yellowstone. Despite the fact that Mock suffered significant scalp and facial wounds, he managed to call 911 after the attack and was found by a search team about 50 minutes later. He was taken to hospital in the city of Idaho Falls but later died.
The last time a person was attacked and killed by a grizzly bear was in 2018 in Wyoming, while grizzlies have killed a total of eight people in the Yellowstone region since 2010. The park, which spans Montana, Idaho and Wyoming, is home to more than 700 bears.
Since 1975, grizzlies have been protected as endangered species outside Alaska after being hunted to the brink of extinction in the early 20th century.