The 22-year-old stepdaughter of actress Patty Duke was killed when the sport-utility vehicle she was driving plunged into a drainage pond for the North Fork of the Coeur d'Alene River.

Raelene Michelle Pearce, 22, a student at North Idaho College in Coeur d'Alene, died early Monday at the scene of the accident about eight miles northwest of the Panhandle community of Kingston, Shoshone County Sheriff's Cpl. Mitch Alexander said.The accident remained under investigation Tuesday.

Alexander said Pearce's vehicle dropped over a 30-foot bank off Bumblebee Road about 6 a.m. Monday and was completely submerged in the icy water. Her passenger, Jeffrey Casey, 23, also of Coeur d'Alene, escaped the wreckage and was picked up by another vehicle passing by.

Casey later was treated for hypothermia and released from Shoshone Medical Center.

The couple had been camping farther up the river and apparently traveled to a local store for supplies. Alexander said they were driving back to the campsite.