For at least eight minutes, a hiker sat within 50 yards of a grizzly bear, taking photos and watching it play in Alaska's Denali National Park.

But suddenly the bear turned on the man, attacking him and mauling him to death, officials said.

The Los Angeles Times reported Park Superintendent Paul Anderson said photos from the man's camera show the bear grazing in the willows and not acting aggressively.

Backpackers are told to stay at least a quarter mile from bears when in the park, he said.

The victim was backpacking alone along the Toklat River when he spotted the bear, officials believe.

The Syracuse said hikers stumbled upon an abandoned backpack, torn clothing and blood along the river about three miles from a rest area on Friday afternoon. The hikers also spotted torn clothing and blood. They immediately alerted staff park.

Rangers in a helicopter spotted a large male grizzly bear sitting on the hiker's remains and a state trooper shot and killed the bear yesterday.

The newspaper said investigators will examine its stomach contents and use other tests to confirm it killed the hiker.

The Sacramento Bee said investigations would try to determine what made the bear turn on the hiker.

"It's an extremely rare event, and it's not common that we even have injuries related to bears," said park spokeswoman Maureen McLaughlin.

"So in terms of what triggered this, we do not know. It was an unwitnessed incident, but we'll see if there are any clues that the biologists can find as to why this took place."