A snowmobile carrying another father and son who rushed to the rescue also cracked through the ice but they managed to clamber out of the frozen water.
"The fog was a big contributing factor in this accident,'' sheriff's Lt. Michael Powers said. "The first snowmobile broke through and the second went to try and help but also broke through."
The victims were identified as Douglas B. Dochterman of Oshkosh and his son, Daniel. Their would-be rescuer, John Leyhe, 41, was in critical condition Tuesday at Mercy Medical Center at Oshkosh. His son Martin, 7, was in good condition at another hospital.
Leyhe said the group had been returning home from ice fishing. He and his son were following the other pair when the group became disoriented in the fog.
Martin Wesenberg, a member of the Otter Street Fishing Club, said the accident happened on a part of the lake where the currents make it dangerous.
"We normally tell people to steer clear of that area," he said.
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