She died after helping her younger cousins out of the raging river.
The victim has been identified as a 53-year-old from rural Bagley.
The suspect was arrested following a search that lasted several hours.
The 18-year-old's identity was released Tuesday afternoon.
The tragedy happened near the Clearwater Dam on Monday afternoon.
The 60-year-old New Hope resident disappeared on Tuesday.
More counties are considering similar gun protection resolutions.
The woman was stabbed in the chest, according to authorities.