A mama grizzly bear with a cub attacked a group of seven teenagers in Alaska Sunday as they crossed a creek as part of a survival course. The teenagers, between the ages of 16 and 18, were on the 24th day of a 30-day backpacking trip in the Talkeetna Mountains—their first day without adult supervision. According to the Anchorage Daily News, they crossed the creek in a line, and the final six campers were still crossing when they heard the first member begin to scream. The bear then attacked another group member before returning to the first. Once the bear retreated, the teenagers administered first aid and activated a rescue beacon. The Anchorage Daily News says the injuries of both campers seriously attacked by the bear—Joshua Berg of New City, N.Y., and Samuel Gottsegen of Denver—are “life-threatening.” The other five teens sustained less serious injuries.