A teenage boy who was critically injured while rappelling down Camelback Mountain on Friday has died.

Phoenix police say 15-year-old Trevor Crouse died Friday evening after being taken to the hospital in extremely critical condition.

Off-duty Phoenix firefighter Gary Johnstone, 50, was also killed in the fall. Authorities say Johnstone, Crouse and another 15-year-old boy were about 200 feet up the Echo Canyon Trail around 7 a.m. when they fell approximately 30 feet. The other boy suffered injuries that were not life-threatening. 

Authorities say it appears they were in the middle of a rappelling or rock climbing maneuver when the accident occurred. Police are trying to determine what led to the fall but have ruled out foul play. 

Johnstone was an engineer paramedic and had spent nearly 25 years in firefighting, including 15 in Phoenix.