"Fat Bear Week" at Katmai National Park, an event celebrating the magnificent grizzly bears and the awe-inspiring sockeye salmon run on the Brooks River, has been marred by tragedy. Two of the park's favorite grizzlies went to war while in the water contesting a salmon. The result was the female sinking beneath the water.

"This morning an adult male bear attacked and killed another bear at Brooks River," Resident Naturalist Mike Fitz said during a live public program. "The incident was witnessed live on the webcams."

"We love to celebrate the success of bears with full stomachs and ample body fat in Fat Bear Week, but the ferocity of bears is real. The risks they face are real. Their lives can be hard, and their deaths can be painful," he added.

“402 was a beloved bear by each and every one of us,” he said during the video discussion. “Honestly, I think we are all at a little bit of a loss of words.”

"Nature is as nature does," wise philosopher Forrest Gump might have said. The bear war delayed proceedings for Fat Bear Week for a day as the entire fight was captured on the live stream. (If nature makes you squeamish, I recommend that you not play the video.)

The attack took place at the mouth of the Brooks River at roughly 9:30 a.m. The location of the attack is significant because it's the one place on the river where there is a large concentration of bears waiting for the salmon. Bears are not very sociable animals, and there are frequent fights as the bears jostle for the best position, although it's very rare for these fights to end in death.

Video footage shows bear number 469 attacking bear number 402 and apparently drowning her after a struggle. (The action begins at around 8 minutes in.)

USA Today:

Wildlife officials, during the live stream, said they don't know why the two bears were fighting, but during "this time of (the) year, bears are in that state of hyperphagia, and they are eating anything and everything they can." They added that they still cannot fathom why one bear would attack another one considering they are not food sources.

"It's uncommon thing to see a bear predating on another bear, but it's not completely out of the question," Katmai National Park ranger Sarah Bruce said. "So, it's hard to say why (and) how this started."

The "March Madness-style" brackets for the completion were to be released on Monday. Instead, they were released on Tuesday.

“Fat Bear Week satisfies your hunger for bears, salmon, and the other wonders of Katmai,” said park superintendent Mark Sturm, “all with one bite.”

The annual competition celebrates the bears’ "success in fattening up for hibernation. Fans vote for the bear that’s put on the most weight over the summer," reports Alaska Public Radio.

“402 was a beloved bear by each and every one of us,” he said during the discussion. “Honestly, I think we are all at a little bit of a loss of words.”

Bear 402 was the mother of eight litters of cubs and was a favorite of "bear cam" fans going into Fat Bear Week. There were nearly 1.4 million votes cast last year during Fat Bear Week from all around the world.