Teton County sheriff's officials say the chopper had reached the snowmobiler, 53-year-old Steven Anderson of Morris, Minn., and his party but was leaving to get more help when it crashed Wednesday.
It went down on Togwotee (TOH'-gut-ee) Pass in northwest Wyoming, about 50 miles northeast of Jackson.
The rescuer killed was 63-year-old rescuer Ray Shriver. The pilot and another rescuer were injured.
