A grizzly bear that emerged from a thicket and charged two backpackers in the backcountry of Denali National Park and Preserve was shot and killed by one of the two who was carrying a .45-caliber semi-automatic pistol, according to park officials.

The killing Friday is believed to be the first instance of a hiker killing a grizzly in the park's wilderness. The killing occurred in the original Mount McKinley National Park portion of the Denali, which was expanded by two-thirds in 1980.

Until February, when Congress changed the rules, it was illegal to carry a loaded firearm in that portion of Denali. While the rule change now allows hikers to carry firearms in all areas of Denali, it still is illegal to discharge them, park officials said.

Park officials did not speculate whether the killing was justified. This is believed to be the first instance of a visitor to a national park killing an animal with a firearm since the gun regulations were changed.

According to a release from the park, the two backpackers, a man and woman, were hiking in dense brush along the edge of Tattler Creek, which is at the west end of Igloo Canyon roughly 35 miles from the park headquarters.

"The man, who was in the lead, drew a .45 caliber semi-automatic pistol when they heard a noise coming from the brush. When the bear emerged from the thicket and ran toward the other hiker, he fired approximately nine rounds in its general direction. The bear stopped, turned, and walked back into the brush, where it quickly disappeared from view," said the release.

The two then headed roughly 1.5 miles back to a road, where they encountered a park employee, who called in the incident and took the two backpackers to the Toklat Road Camp. A ranger there did a short preliminary interview with them at approximately 10:00 p.m. Because of the concern that a wounded bear was in the area, four backcountry units were immediately closed, and bus drivers were instructed to not drop off day hikers in the Igloo Canyon on Saturday.

"Early Saturday morning rangers and wildlife technicians flew to Toklat via helicopter to conduct a secondary interview with the two backpackers. Afterwards they flew over Tattler Creek and all of side tributaries, very low at times, to determine if there was an active, wounded bear," the park release said. "No bears were seen during the overflight, and late in the afternoon three rangers hiked into the site. The bear was found dead in a willow thicket approximately 100 feet from the pistol casings at approximately 6:00 p.m.

"The bear’s body was transported via helicopter to a landing site on the park road and brought back to headquarters on Sunday, where park wildlife biologists are assisting with the investigation of the bear carcass. The backcountry units have been reopened."

The case is still under investigation, and the names of the backpackers are not being released at this time. Park wildlife biologists and rangers are trying to determine if there was a justification for shooting the animal.

The estimated grizzly bear population in the park north of the Alaska Range north is 300-350 animals.