Editor's note: This update provides information on efforts to trap the bear, additional details on Mr. Wallace's itinerary in the park.

Efforts were under way Monday to try to trap a grizzly bear that fatally mauled a Michigan man on a day hike in Yellowstone National Park.

The fatal mauling was the second in the park this year.

The body of 59-year-old John Wallace, of Chassell, Michigan, was spotted along the Mary Mountain Trail by two other hikers Friday afternoon.  The man apparently died earlier in the week, possibly Wednesday or Thursday, park spokesman Al Nash said Sunday.

At the time, citing the ongoing investigation, he could not say whether there were any obvious signs of trauma or attack by an animal. While there were signs of grizzly bear activity at the scene, he said, an aerial search of the area Saturday morning failed to turn up any current bear activity.

An autopsy on Sunday, however, determined that Mr. Wallace, who was traveling alone, suffered traumatic injuries that had been inflicted by a grizzly, Mr. Nash said Monday.

The Michigan man, who had camped in a front-country campground on Wednesday, was on a day hike on the Mary Mountain Trail when he was killed, the park spokesman said.
However, investigators were not immediately able to piece together whether it was a random attack or whether the man had startled a sow with cubs.

“Because there’s no witnesses, there’s a limit to what we’re able to figure out," Mr. Nash said.

The 21-mile-long Mary Mountain Trail crosses the center of Yellowstone, connecting the west and east sides of the lower portion of the Grand Loop Road. Mr. Wallace's body was found about 5 miles west of the Hayden Valley trailhead, which is off the Grand Loop Road between Mud Volcano and Canyon Junction.

Park officials have closed both the Mary Mountain Trail, the Cygnet Lakes Trail, and the section of the Hayden Valley west of the Grand Loop Road to hikers in the wake of the incident. They also were setting traps to see if they might be able to catch the bear responsible for the man's death.

"We do have some traps set out in Hayden Valley to see if it is possible to capture a bear. If we’re successful, then we’ll attempt to determine if it is 'the' bear," Mr. Nash said. Those efforts would involve taking DNA samples from any captured bear's hair, as rangers were able to recover some hairs from the site of the mauling, he said.

Visitors are advised to stay on designated trails, hike in groups of three or more people, be alert for bears, make noise, carry bear spray, and not to run upon encountering a bear.

Hikers and backcountry users are encouraged to check with staff at park visitor centers or backcountry offices for updated information before planning any trips in the central portion of the park.

In the first mauling this summer, Brian Matayoshi, 57, of Torrance, California, was killed by a sow grizzly that had two cubs nearby. Mr. Matayoshi and his wife had been hiking along the Wapiti Lake Trail, which is located off the South Rim Drive south of Canyon Village and east of the park’s Grand Loop Road, when they encountered the bears in early July.

"It appears that the couple spotted a bear approximately 100 yards away and then began walking away from the bear. When they turned around to look, they reportedly saw the female grizzly running down the trail at them," a park release said at the time. "The couple began running, but the bear caught up with them, attacking Mr. Matayoshi. The bear then went over to Mrs. Matayoshi, who had fallen to the ground nearby. The bear bit her daypack, lifting her from the ground and then dropping her. She remained still and the bear left the area."

A Board of Review convened to examine that incident has yet to file its report.

Mr. Nash could not recall the last time, if ever, that there were two fatal bear maulings in the park in one summer.

“We don't normally have two people injured by a bear in a year," he said.