A backcountry guide was mauled to death by a grizzly bear near Yellowstone National Park

• Charles "Carl" Mock, 40, of West Yellowstone, Montana, was attacked by a bear near Yellowstone.
• He died two days after being seriously injured in the bear attack.
• Investigators believe the bear was defending a food source when it mauled Mock.

A backcountry guide was mauled to death by a grizzly bear while fishing near Yellowstone National Park, according to a release from the Montana Fish, Wildlife and Parks Department.

Charles "Carl" Mock, 40, was fishing on Thursday just north of West Yellowstone, Montana, and close to the national park when the bear attacked.

"The man had bear spray with him, but it's unclear whether he was able to deploy it during the attack," Montana Fish, Wildlife and Parks Department said, adding that investigators believe the bear was defending a food source when it mauled Mock.

Mock transported to Idaho Falls for treatment, but after two surgeries and a stroke, he died on Saturday from injuries he sustained in the attack, Backcountry Adventures, Mock's employer, said in a Facebook post.

The bear was shot and killed by Montana Fish, Wildlife & Parks staff on Friday after they determined the animal was an "immediate safety risk."

Grizzly bears have injured 44 people in Yellowstone since 1979, while hosting over 118 million visits in the same time period, the National Park Service told CNN.