The teens had been advised to play dead if they encountered a grizzly during their excursion in the Alaska wilderness.
But with the massive, snarling bear suddenly looming over them, 17-year-old Sam Gottsegen of Denver and the other participants of a backcountry survival course did what so many others would have done: They ran.
The bear pounced on some of the students, including Gottsegen, who was among four seriously injured.
"When I heard that bear, when I saw it, it was all just like natural instincts," he said. "All night long I was thinking I should have played dead."
The attack Saturday night in the Talkeetna Mountains north of Anchorage came as the group of seven was nearing the end of the 30-day survival course. The teens were at a stage where they could try out their skills without adults around.
Playing dead after seeing a grizzly was part of the training, said Don Ford, the Alaska director of the National Outdoor Leadership School, the group that operated the backcountry program.
"We recognize people are going to react differently," he said Monday at a news conference in Palmer. "You don't know how we're going to react. The bear came really fast, that's was super unusual."
The students were yelling as well, alerting bears possibly in the area that there were humans nearby, Ford said. But this bear might not have heard them because of a rock outcropping in the area, he said.
As the grizzly furiously thrashed him about, all Gottsegen could think about was what he would miss: college, traveling, life.
"I thought: 'I'm going to die,'" he told The Associated Press from his hospital bed in Anchorage. "I thought, 'This just can't be happening to me.'"
Then the bear left, only to return a moment later to continue mauling him and his other teenage friends. Only three in the group escaped without injury.
Authorities believe the bear was aggressive because it was with its cub. Gottsegen said no one ever saw a cub.
The group was hiking through bushes that got so thick they decided to wade through a river, walking in single file. Around a bend in the river, Joshua Berg, 17, of New City, N.Y., began yelling "Bear! Bear!"
The bear took him down first. The animal made angry, growling noises as it attacked, Gottsegen said.
It was so sudden. There was no time to pull out their bear deterrent spray, and no one had a gun. Berg, badly wounded, called for someone to set off the personal locator beacon they carried for emergencies.
When Gottsegen was attacked, he kicked at the grizzly, to no avail.
Then the bear struck him, biting him on the head, lashing out at the teen's arms and chest, puncturing a lung and breaking two ribs. The attack on the group probably lasted less than a minute, he said.
Shane Garlock, who was uninjured, said Monday that the sounds of the attack are what haunt him.
"Whenever I tell this, I usually outline the screaming that I could hear from my friends and the growls from the bear, which were loud and deep, and the screams, which were hopeless screaming, and I can still hear it in my head," he said.
After it was over, it started raining.
The teens set up a camp and tended to the injured, making good use of their survival skills. They plugged a deep wound in Gottsegen's torso with a plastic trash bag secured with an Ace bandage.
They also activated the beacon.
Patricia Allaire, the mother of another injured student, Noah Allaire, 16, of Albuquerque, N.M., said her son initially tried to activate the beacon, thinking the bear was gone, but then it struck again.
The bear thrashed the teen's head and back and slightly puncturing a lung. He was listed in good condition Monday at a hospital.
Authorities received the signal around 9:30 p.m. Saturday, and dispatched rescuers, including Alaska State Troopers. Megan Peters, a troopers spokeswoman, praised the teens for doing their best to take care of each other.
"It speaks great volume to their character that they were able to come together like this after such a devastating encounter," Peters said. "They came face-to-face with the worst Alaska had to offer, and they're able to say they survived it."
A trooper and pilot in a helicopter located the students in a tent shortly before 3 a.m. They decided the two most seriously injured would need a medical transport aircraft.
The trooper and another student stayed with the badly injured teens for a couple hours until more rescuers arrived in a specially equipped helicopter, Gottsegen said.
The uninjured student who remained was 16-year-old Samuel Boas of Westport, Conn.
Boas has training as an emergency medical technician, said Bruce Palmer, the spokesman for the Lander, Wyo.-based National Outdoor Leadership School.
"The first aid was good, we got good feedback from the Alaska State Troopers, from the hospital, the Air National Guard," Ford said of the way the teenagers reacted after the attack. "They really pulled it together, and did a real good job."
The other student injured was Victor Martin, 18, of Richmond, Calif., who was treated at a hospital for a bite wound above his ankle and then released, according to Palmer.
The teens were in the 24th day of their course when the attack occurred.
Berg remained in serious condition Monday, while Gottsegen was upgraded to good from serious.
Berg's parents Liz Breyer and William Berg said in a statement their son continues to improve.
"We're grateful to the surgeons, physicians and nurses who are caring for our son," they said. "We appreciate the efforts of the Alaska State Troopers, Alaska Air National Guard, and Josh's fellow National Outdoor Leadership School students who helped him. We are so thankful for the outpouring of love and support from our family and friends."
Associated Press writer Mark Thiessen contributed to this report.