Australian Twin Sisters Shot at Colorado Range: Was it a Suicide Pact?

AURORA, Colo. (CBS/KCNC/AP) Investigators remained baffled Wednesday over a bizarre case in which twin sisters from Australia were mysteriously found at a shooting range south of Denver with gunshot wounds to the head.

They are trying to determine what happened to the 29-year-old sisters who came to the U.S. on cultural exchange visas: was it a shootout, a failed murder-suicide or a suicide pact?

Complicating matters is the fact that investigators have had difficulty determining which sister died because they look so much alike. One sister was killed, and the other was upgraded Wednesday from critical to serious condition.

According to CBS affiliate KCNC, the medical condition of the surviving sister was determined to be too grave to undergo questioning about what happened.

Doug Hamilton, the owner of the Family Shooting Center at Cherry Creek State Park, told KCNC that the sisters were in good spirits and adept at shooting the small-caliber handguns.

Hamilton says he is confident the shooting was planned.

"It was not an accident. It was a deliberate shooting," he said.