ANCHORAGE, Alaska - The teenage outdoor education students, having progressed to the point of being on their own in the vast Alaska wilderness, were lined up single file for a river crossing when the grizzly burst with fury into the front of the line, badly mauling two in the group and injuring two more. Hospital spokeswoman Crystal Bailey said the two mauled teens are listed in serious condition after troopers earlier said the injuries were life-threatening. Those in the front screamed of the bear's presence. The bear was with her cub when she attacked, according to state troopers. The teens were in a group of seven participating in a 30-day backcountry course conducted by the National Outdoor Leadership School when the attack occurred Saturday night in the Talkeetna Mountains north of Anchorage. They were rescued early Sunday after activating their emergency locator beacon and tending to their most seriously wounded. The group was eventually found about 34 miles away from the nearest highway, CBS News affiliate KTVA-TV reports. Those in the back of the line heard the warning, with the two at the front of the line taking the brunt of the attack, trooper spokeswoman Megan Peters said. Another group of seven students and three instructors was waiting about six miles away for a helicopter hired by the Lander, Wyo.-based NOLS, said Bruce Palmer, a spokesman for the organization, which leads many such excursions in Alaska and elsewhere. Palmer said the worst injured with bear bite wounds are 17-year-old Joshua Berg of New City, N.Y., and 17-year-old Samuel Gottsegen of Denver. They were being treated at Providence Alaska Medical Center in Anchorage. Gottsegen had suffered a punctured lung, broken ribs and head and chest wounds when the bear came back for more, CBS News' Danielle Nottingham reported on "The Early Show." That's when Berg intervened, probably saving Gottsegen's life. "[He] came up and started kicking the bear to help Sam fight the bear off, and the bear then went away, so ... I'm extremely grateful," Mindy Gottsegen, Samuel's mother, told CBS News. When the bear broke off the attack, the teens activated a personal locator beacon they carried to be used only for an emergency, Peters said. The Rescue Coordination Center operated by the Alaska Air National Guard called troopers around 9:30 p.m. to report the activated signal. A trooper and pilot in a helicopter located the students in a tent shortly before 3 a.m., but decided the two most seriously injured would need a medical transport aircraft with a medically trained crew. The first responders called the rescue center for help and then flew four of the teens to the Talkeetna airport. From there, they were driven by ambulance to the hospital in Palmer, a community about 40 miles northeast of Anchorage, where they were given additional emergency treatment. The trooper and another student stayed with the badly injured teens for four hours until more rescuers arrived in a specially equipped helicopter, which flew them to the Anchorage hospital, Peters said. The uninjured student who remained was 16-year-old Samuel Boas of Westport, Conn. Palmer said Boas has training as an emergency medical technician The other students injured were Victor Martin, 18, of Richmond, Calif., who was taken to Mat-Su Regional Medical Center in Palmer and released after being treated for a bite wound above his ankle, according to Palmer, and Noah Allaine, 16, of Albuquerque, N.M.. Allaine remained at the Palmer hospital with injuries Palmer said he did not know. Allaine was listed in good condition, according to a hospital spokeswoman, Margo Wesley. The teens were in the 24th day of their course when the attack occurred. There was no instructor with them because that far into the course, they've learned enough survival skills, Palmer said. "Our basic goal is that when a student graduates from the NOLS course, they have the experience and background to be able to take other people out into the backcountry," he said. "We're training people to be outdoor leaders basically." Calling out to alert bears of human presence and give nearby animals a chance to flee is among the skills learned in the course. "The students say they were" doing that, Palmer said. The teens told troopers the 8:30 p.m. attack occurred as they prepared for a river crossing. The bear attacked Berg first, turned to another student, then turned back to Berg, Palmer said.