Police want to know the identity of this little girl, who appears to be 4 or 5.

1 of 3 The tape was turned in to police by a man who said he found it in the desert.

It shows a man performing sex acts on a girl around 4 or 5 years old, and shows a girl believed to be 10 to 12 years old appearing in "some kind of peep show," said Nye County sheriff's detective David Boruchowitz.

Authorities hope identifying the girls will help them locate the abuser.

Still photos of the younger girl, fully clothed, have been widely broadcast. Boruchowitz announced Thursday that the older girl had been identified.

He said the photos of the younger girl were being released because her life could be in danger.

"She could still be in this situation and (be) abused currently as we speak," Boruchowitz said.

"The easiest way to explain it is if you can imagine the absolute worst things that can happen to a little girl at the hands of an adult male, that has happened and beyond," he said of the video. "It is by far the most heinous and horrible thing that you can possibly imagine on there." Watch authorities describe the disturbing case »

The older girl did not appear to have been sexually abused on the tape and the footage appeared to have been shot from a different room, Boruchowitz said.

Investigators were examining whether the two segments were filmed with the same video camera, he said.

A 26-year-old Pahrump man, Darren Tuck, surrendered the tape to Nye County sheriff's investigators September 8, after another man reported seeing it, Boruchowitz said.

Tuck told detectives he found the videotape in the desert outside Pahrump more than five months ago, although Boruchowitz said the tape didn't appear to have been exposed to weather or elements.

Investigators think the tape is less than two years old, a sheriff's office official told CNN.

Boruchowitz said investigators don't think Tuck made the tape. Tuck was arrested September 19 on charges of promoting child pornography and possession of child pornography, felonies. The top charge carries a possible sentence of up to life in prison.

Tuck was released without bail, pending arraignment November 26 in Pahrump Justice Court, a court official said.

Pahrump is a small town 60 miles west of Las Vegas. E-mail to a friend

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