We're going to turn now to a story of heroism that's turned to tragedy. A 6-year-old boy, falling into a raging river, and then saved by two people who jumped in. But his rescuers vanished in the... See More
We're going to turn now to a story of heroism that's turned to tragedy. A 6-year-old boy, falling into a raging river, and then saved by two people who jumped in. But his rescuers vanished in the dangerous waters. Abc's john schriffen with the latest on that river rescue in south dakota. Reporter: All day, rescuers frantically searched through this thick foam covering the big sioux river in south dakota for 16-year-old madison wallace, who jumped in last night to save her 6-year-old brother, garrett. We don't really have an exact cause as why he went in the water. Though, last night, the foam that you see here last night, it was up to ten feet deep. Reporter: Authorities broke through the ice and hosed down the foam to get a clear line of sight. The foam is common this time of year, caused by the runoff upstream mixing with chemicals. Late this evening, they pulled madison's lifeless body from the water. We did find the young girl who went in after her brother. We found her near an area we thought we'd be looking for. Reporter: They are still looking for a 28-year-old man who jumped in to help her. A good samaritan now presumed dead. John schriffen, abc news, new york.
This transcript has been automatically generated and may not be 100% accurate.