NATIONAL PARKS --  A grizzly bear killed a hiker today on a popular trail in the Yellowstone National Park backcountry. It's the first fatal bear mauling in the park since 1986, officials said.

Park spokesman Al Nash said it appears the man and his wife surprised a female grizzly and her cubs this morning, the Associated Press reports.

Nash said investigators have been interviewing the woman about the bear attack, which took place close to Canyon Village, near the middle of the park. He said authorities aren’t prepared to release the man’s name, age or hometown and likely won’t release more details until Thursday.

Nash said park officials haven’t taken any action against the bear, which he described as a sow with cubs.

Read on for details.

The unidentified couple were about a mile and a half from the trailhead of the Wapiti Lake trail when they encountered the sow and her cubs, the Los Angeles Times reports.

The bear, apparently reacting to the perceived threat to her cubs, fatally attacked  the man, park officials said. The woman was unhurt.

Nearby hikers heard the woman's cries and used a cellphone to call for help. The victim died at the scene. Yellowstone law enforcement and emergency medical personnel responded, as did a park employee who serves as a coroner.

Rangers closed all trails and backcountry campsites in the area, which is southeast of Canyon Village. Rangers on foot patrol swept the region for any hikers. The area is is a gateway to the Pelican Valley, where it is common to see bears. A bear-warning sign was posted at the Wapiti Lake trailhead.

It was the first bear-caused human fatality in Yellowstone in nearly 25 years, according to park officials.

Yellowstone spokesman Al Nash said there had been no reports of grizzly encounters in the park, which is just emerging from a heavy winter. Wildlife researchers in the upper Rockies have theorized that with declining grizzly habitat and fewer food sources, bears might become more prone to attack humans. But Wednesday's incident appeared to be an act of defense by the bear, which fled with her cubs.

The last fatal grizzly attack in Yellowstone was in October 1986, when the mauled body of a man was found by the road near Otter Creek. A camera and tripod were nearby, causing park officials to conclude that the man was attacked while he was photographing a grizzly