Police then spotted the woman and her 6-year-old, Dakota, at the edge of the brook, about 100 yards away from the parents' home.
Officials say Waring waded into the water with the child and stayed out of the reach of a police officer who was trying to rescue them.
Waring and the child were then swept downstream.
Police say it was a "deliberate action," but have stopped short of calling it a suicide.
The bodies of Waring and the 6-year-old have been recovered. Officials are now searching for Warning's other daughter, 2-and-a-half-year-old Grace.