Couch, 32, has evaded capture since Saturday, after he allegedly used an AR-15 to shoot at unsuspecting drivers on Interstate 75, near London, Kentucky, according to the FBI.
The children were between 13 and 18 years old, and were recovered in Cleveland and Akron, Ohio. One victim was found in Washington state.
The Attorney's Office defined third-degree murder as someone causing another's death "by perpetuating an act eminently dangerous to others and evincing a depraved mind, without regard for human life."
Police in Beaverton, Oregon, announced the discovery of 32-year-old Melissa Jubane's remains Saturday, after family first reported her missing three days prior.
