Brian Matayoshi, 57, was mauled and killed by the bear, which then picked up his wife Marilyn by her backpack before dropping her and leaving with its two cubs, said Tuesday's official report, accompanied by a recording of 911 calls.
The couple encountered the mother bear with her cubs on the Wapiti Lake Trailhead, a popular route in the sprawling park, which spans the US states of Wyoming, Montana and Idaho, on the morning of July 6.
The bear was about 100 yards away when they noticed it and turned around to get away. Looking over their shoulders, they saw it was following them and began to run and yell, the report on the park's website said.
"The bear's chase response to the Matayoshis was most likely exacerbated by their running and yelling as they fled," it said.
"What possibly began as an attempt by the bear to assess the Matayoshis' activities became a sustained pursuit of them as they fled running and yelling on the trail."
The report noted that signs at the start of the trail indicated the presence of bears and gave the standard advice not to try to run if approached by a bear, but to carry pepper-spray.
The Matayoshis did not carry pepper-spray, according to the report, which was posted with a recording of two 911 calls to emergency services made by another nearby hiker.
The hiker reported initially hearing a man making noises "like an animal" in an apparent attempt to scare the bear, and a woman's shouts.
Later he could only hear the woman's cries for help, after her husband had been mauled.
In a separate attack in the park, a 59-year-old man from Michigan died in August after being mauled by a grizzly bear while camping alone in Wyoming.